Additive Manufacturing for Occupational Hygiene: A Comprehensive Review of Processes, Emissions, & Exposures

AB Stefaniak; S Du Preez; JL Du Plessis

doi:10.1080/10937404.2021.1936319

. Author manuscript; available in PMC: 2022 Dec 17.

Published before final editing as: J Toxicol Environ Health B Crit Rev. 2021 Jun 17:1–50. doi: 10.1080/10937404.2021.1936319

Additive Manufacturing for Occupational Hygiene: A Comprehensive Review of Processes, Emissions, & Exposures

AB Stefaniak ^a,^†, S Du Preez ^b, JL Du Plessis ^b

PMCID: PMC8678392 NIHMSID: NIHMS1717812 PMID: 34139957

Abstract

This comprehensive review introduces occupational (industrial) hygienists and toxicologists to the seven basic additive manufacturing (AM) process categories. Forty-six articles were identified that reported real-world measurements for all AM processes, except sheet lamination. Particles released from powder bed fusion (PBF), material jetting (MJ), material extrusion (ME), and directed energy deposition (DED) processes exhibited nanoscale to submicron scale; real-time particle number (mobility sizers, condensation nuclei counters, miniDiSC, electrical diffusion batteries) and surface area monitors (diffusion chargers) were generally sufficient for these processes. Binder jetting (BJ) machines released particles up to 8.5 μm; optical particle sizers (number) and laser scattering photometers (mass) were sufficient for this process. PBF and DED processes (powdered metallic feedstocks) released particles that contained respiratory irritants (chromium, molybdenum), central nervous system toxicants (manganese), and carcinogens (nickel). All process categories, except those that use metallic feedstocks, released organic gases, including (but not limited to), respiratory irritants (toluene, xylenes), asthmagens (methyl methacrylate, styrene), and carcinogens (benzene, formaldehyde, acetaldehyde). Real-time photoionization detectors for total volatile organics provided useful information for processes that utilize polymer feedstock materials. More research is needed to understand 1) facility-, machine-, and feedstock-related factors that influence emissions and exposures, 2) dermal exposure and biological burden, and 3) task-based exposures. Harmonized emissions monitoring and exposure assessment approaches are needed to facilitate inter-comparison of study results. Improved understanding of AM process emissions and exposures is needed for hygienists to ensure appropriate health and safety conditions for workers and for toxicologists to design experimental protocols that accurately mimic real-world exposure conditions.

Keywords: Process descriptions, 3D printing, particles, gases, monitoring, research needs

Introduction

Additive manufacturing (AM) is the process of joining feedstock materials to make parts from a computer file (ISO/ASTM 2015). Parts made by AM are usually built using layer-upon-layer addition of feedstock material, which differs from traditional subtractive manufacturing where material is selectively removed to make a part or formative manufacturing methodologies where material is forged or molded to make a part. AM has been used for rapid prototyping and manufacturing since the early 1990s (Bourell 2016).

In 2004, a case of allergic dermatitis was reported in a worker who operated a vat photopolymerization machine (Chang et al. 2004), which to our knowledge was the first report of an adverse health effect associated with an AM exposure. When key patents on fused deposition modeling (FDM^™) material extrusion machines expired in 2005, there was a surge in availability of low-cost machines that utilize fused filament fabrication (FFF) technology, what is now commonly referred to as 3D printers (Ford 2014). AM is colloquially referred to as 3D printing; however, these are technically different. The term 3D printing has generally referred to machines that were low end in price and/or capability (ISO/ASTM 2015), most commonly those based on FFF technology, which is one variation of the material extrusion AM process category.

The availability of low-cost FFF 3D printers has led to a rise in their use for various industrial applications as well as in offices, classrooms, libraries, homes, and other non-industrial spaces. Stephens et al. first reported that FFF 3D printers emitted ultrafine particles (diameter < 100 nm) at rates that exceeded 10 billion particles/min in an office space (Stephens et al. 2013), which brought AM to the widespread attention of the occupational (industrial) hygiene community and set off a cascade of research on the topic. Though AM is gaining popularity in many industries (Ford 2014; Wu et al. 2020), some occupational (industrial) hygienists and toxicologists may not be familiar with all types of AM process categories and the substances released from these processes. Further, approaches to measure substances that are released into indoor air need clarification for appropriate selection of measurement methods for exposure assessments. Identification of appropriate measurement methods is also needed for design of toxicology studies to ensure exposures are based on real-world exposure conditions. Hence, the purposes of this comprehensive review were to: 1) introduce occupational (industrial) hygienists and toxicologists to the seven basic AM process categories, 2) summarize available data on substances that are released from each of these process categories, 3) critically evaluate approaches used to characterize releases (emission rates [ERs] and concentrations), and 4) identify research needs to more fully understand emissions and exposures.

Additive manufacturing process categories

Based on internationally harmonized terminology, there are seven basic AM process categories:

binder jetting (BJ) – a liquid bonding agent is selectively deposited to join powder,
directed energy deposition (DED) – focused thermal energy is used to fuse materials via melting as they are deposited,
material extrusion (ME) – material is selectively dispensed through a nozzle or orifice,
material jetting (MJ) – droplets of build material are selectively deposited,
powder bed fusion (PBF) – thermal energy selectively fuses regions of a powder bed,
sheet lamination (SL) – sheets of material are bonded to form a part, and
vat photopolymerization (VP) – liquid photopolymer in a vat is selectively cured by light-activated polymerization (ISO/ASTM 2015).

An AM system consists of a machine and associated equipment needed to manufacture a part. Within an AM system, the build chamber is the location where the part is made and it is often, but not always, enclosed. Historically, the purpose of an enclosed build chamber was to maintain necessary conditions during a build cycle (e.g., atmospheric thermal stability). Some manufacturers now sell enclosed AM systems with filters intended for exposure mitigation (Katz et al. 2020). Within the build chamber, parts are built on a build platform, which depending on the process may be positioned in a horizontal or vertical orientation and may or may not be heated. For DED, ME, MJ, SL, and VP the part is built attached to the build platform (directly or via support material) whereas in BJ and PBF the part is built in a powder bed and is not fixed to the build platform (ISO/ASTM 2015).

All AM parts are built from feedstock, which is the building material supplied to an AM process. As summarized in Table 1, feedstock may be in the form of solid powder, filaments, pellets and sheets or liquid resins. Some feedstock materials contain wood, metals, clays, carbon or glass fibers, ceramics, engineered nanomaterials, flame retardants or other additives and fillers for functional or esthetic purposes (Ivanova, Williams, and Campbell 2013; Wu et al. 2020).

Table 1.

Physical and chemical characteristics of AM process feedstock materials. Adapted from cit.(ISO/ASTM 2015; Wu et al. 2020).

Process	Physical state	Chemical composition
Binder jetting	Solid powder	Polymers, metals, ceramics, composites
Directed energy deposition	Solid wire	Metals
Material extrusion	Solid filament or pellets	Thermopolymers^a
Material jetting	Liquid resin	Photopolymers^a
Powder bed fusion	Solid powder	Polymers, metals, ceramics, composites, glasses
Sheet lamination	Solid layers	Polymers, metals, ceramics, composites, papers
Vat		photopolymerization
Liquid resin	Photopolymers^a

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May contain metals, ceramics, composites, nanomaterials, or other additives

Binder jetting

From Figure 1(a), the basic operating principle of a binder jetting machine is as follows: 1) a blade spreads a thin layer of powder over the build platform, 2) a carriage with nozzles selectively deposits droplets of a binder in a pattern onto the powder to bond the particles together via a chemical reaction, 3) the powder bed is lowered incrementally and the blade spreads a fresh layer of powder on top of the hardened powder, 4) binder is again selectively deposited onto the powder bed and hardens the next layer of particles, and 5) the process is repeated until the final build cycle is built (Afshar-Mohajer et al. 2015). The final part is submerged in a powder “cake” and is recovered manually. For some machines, the feedstock powder and a liquid activator are mixed, and the binder is applied to the mixture to harden the material, whereas in others an activator and binder are mixed then sprayed onto the powder to harden the material. For this AM process category, pre-printing tasks include loading powder in the machine, post-printing tasks include opening machine doors and de-powdering printed parts, and post-processing might include spray coating of printed parts.

Directed energy deposition

In DED, the focused thermal energy source is a laser, electron beam, plasma, or electric arc. Feedstock materials are either in wire or powder form. From Figure 1(b), for wire, the feedstock is 1) fed into the path of the thermal energy source, where it 2) melts and drips onto the build platform in a molten pool and cools and hardens to form a shape. For powder, the feedstock is dispensed via a nozzle. The outer ring of the nozzle dispenses the powder and the inner ring is a laser, which melts the powder and sprays it onto the build platform. For flammable metal powders such as titanium, an inert atmosphere must be maintained in the build chamber (e.g., kept under vacuum or purged with nitrogen or argon gas or local inert gas shielding at the build platform similar to welding) and the AM machine must be properly bonded and grounded to prevent oxidation and fire (Bau et al. 2020). For DED, pre-printing tasks include loading wire or powder into the machine, post-printing tasks include opening machine doors to retrieving printed parts and cutting parts from the build platform, and post-processing can include machining operations to achieve final part dimensions.

Material extrusion

From Figure 1(c), solid polymer is 1) heated to just above its glass transition temperature and dispensed on a build platform, 2) layer-upon-layer to build a part. Numerous polymers are commercially available for ME, and each has unique properties such as thermal stability and chemical resistance (Wu et al. 2020). Variations of ME include fused deposition modeling (FDM^™), a technique created and trademarked by Stratasys Inc., FFF, and large format additive manufacturing machines. Though FDM^™ and FFF are similar, FDM^™ generally refers to industrial-scale machines with enclosed heated build chambers, whereas FFF refers to lower cost desktop-scale ME-type 3-D printers (Bourell 2016; Ford 2014). FFF 3D printers with modified extruder nozzles are used for bioprinting with cells to create 3D tissue models for pre-clinical medical research, pharmaceutical drug discovery, and toxicity testing, e.g., screening of chemicals for irritancy (Ma et al. 2018; Shahin-Shamsabadi and Selvaganapathy 2019; Wei et al. 2020). Pre-printing tasks include loading polymer into machines as filament or pellets, post-printing tasks include opening machine doors to retrieve printed parts, and examples of post-processing tasks are acetone vapor polishing (AVP) and chloroform vapor polishing (CVP) and sanding printed parts.

Material jetting

For MJ, liquid photopolymer resin is 1) dispensed onto a build platform via hundreds of micronozzles, 2) cured using an ultraviolet laser, and 3) the process repeated layer-by-layer to build a part (Figure 1(d)). Numerous resins are available commercially in a range of colors without and with additives that impart specific properties such as flexibility, surface appearance, etc. Pre-printing tasks include loading resin containers into the machine (exposures are expected to be low since most machines use a sealed container loading system), post-printing involves removing printed parts from the build platform, and post-processing usually includes washing (sometimes with ultrasound treatment) by submerging the part in water, followed by rinsing in a caustic bath.

Powder bed fusion

As shown in Figure 1(e), there are two main types of PBF processes, selective laser melting (SLM) that uses as a laser as the energy source and electron beam melting (EBM) that uses an electron beam as the energy source (Zhang et al. 2018). Historically, PBF was referred to as selective laser sintering (SLS), though this term is incorrect because the powder feedstock is fully or partially melted, not sintered (which involves using a mold and heat and/or pressure) (ISO/ASTM 2015). For SLM/SLS: 1) a blade spreads a thin layer of powder over the build platform, 2) a laser is reflected onto the powder using a mirror and it is selectively melted, 3) the powder bed is lowered incrementally and the blade spreads a fresh layer of powder on top of the previously hardened surface, and 4) the process is repeated until the final build cycle is complete. In EBM, a high-powered electron beam selectively melts powder feedstock under near-vacuum conditions: 1) a rake pushes a layer of powder over the build platform, 2) an electron beam is focused using a lens system and selectively melts the powder, 3) the powder bed is lowered incrementally and the rake pushes a fresh layer of powder on top of the previously hardened surface, and 4) the process is repeated until the final object is built (Wu et al. 2020). Upon completion of the final build cycle, the part is encased in powder (referred to as a “cake”) and must be recovered manually. An inert atmosphere must be maintained in the build chamber and the AM machine must be properly bonded and grounded to prevent oxidation of feedstock powder. Examples of PBF pre-printing tasks include powder weighing, mixing, and loading into the machine. Examples of post-printing tasks are opening the machine to retrieve a printed part, de-powdering (e.g., vacuuming) excess powder from the build platform, removing the build platform with attached printed part from the machine, and sieving used powder and refilling the machine. Post-processing tasks include cutting the printed part from the build platform and grinding.

Sheet lamination

In SL, a single 2-dimensional layer of feedstock material is placed on a build platform (also called a cutting bed for this process) and successive layers are added until the final build cycle is complete (Figure 1(f)). Feedstock materials include 2-dimensional sheets of paper or polymer, ceramic tape, and metal in the form of tape, films, or ribbons. Variations of SL include computer-aided manufacturing of laminated engineering materials (CAM-LEM), laminated object manufacturing (LOM), plastic sheet lamination (PSL), selective deposition lamination (SDL), ultrasonic additive manufacturing (UAM), and ultrasonic consolidation (UC). These techniques differ in how they form and bond layers and are generally categorized as “form-then-bond” processes where, as shown in Figure 1 (f), the 1) feedstock is cut to shape (pre-printing task), 2) then bonded to the previous layer (printing task) to 3) form a part (e.g., CAM-LEM) and “bond-then-form” processes where 1) feedstock is bonded (printing task), 2) then cut using a laser or blade or by milling during the build or after the last build cycle (post-processing) to 3) form a part (e.g., SDL, UAM, UC). The technique used to bond layers of feedstock vary and include adhesives (e.g., LOM, SDL, PSL) and ultrasonic welding (UAM).

Vat photopolymerization

The main components of photopolymer resin for VP printers are binders, monomers, and photoinitiators (Wu et al. 2020). As shown in Figure 1(g), variations of VP technology include, but are not limited to, stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD) (Wu et al. 2020; Zhang et al. 2018). SLA printers 1) scan a laser beam across the print area to 2) selectively cure resin on the bottom of a vat as series of points and rounded lines to build objects. DLP printers 1) use a high-resolution projector to flash black and white image slices of each object layer across the entire bottom surface of the vat at once, the projector is a digital screen that forms white areas of the projected image made of square pixels that are 2) cured using UV or multi-wavelength light from a lamp to build a part (Wu et al. 2020). LCD printers are similar to DLP technology, in that they 1) also flash complete layers at the resin on the bottom surface of the vat; however, the light source is UV light from an array of light-emitting diodes shining through a liquid crystal display not a projector and 2) a screen is used as a mask that reveals only the pixels necessary for the current layer to be hardened. VP machines either use a “top-down” or “bottom-up” approach to build a part, though the former is more common (Wu et al. 2020). In “top-down” machines: 1) the build platform is lowered into the vat until it almost touches the bottom of the reservoir, leaving a thin layer of resin between the platform and vat, 2) a light source is aimed up at the build platform and hardens the resin, 3) the platform is incrementally raised to allow a new layer of resin to fill the gap between the platform and bottom of the vat, and 4) the light source hardens the new layer of resin and the process repeated until the last build cycle is complete (Wu et al. 2020; Zhang et al. 2018). In the bottom-up approach: 1) a build platform is submerged just below the surface of the resin in a vat, 2) a light source is aimed down at the build platform and hardens the resin, 3) the platform is incrementally lowered and a roller pushes a new layer of resin across the previously hardened layer, and 4) the light source hardens the new layer of resin and the process repeated until the last build cycle is complete. Regardless of approach, the first solidified layer is attached to the build platform not the vat surface. For all variations of VP, pre-printing tasks include mixing and dispensing resin into vats (can be done outside of the machine or inside the machine) and/or loading a pre-filled vat into the machine. Post-printing tasks include opening the machine to retrieve the printed part, UV-curing to harden unreacted monomers, and ethanol cleaning to remove resin from part surfaces. Post-processing tasks can include sanding and drilling of the manufactured part.

General occupational hygiene considerations

AM applications and uses are rapidly growing; however, to date only a few publications have addressed worker safety and health. Deak (1999) first expressed the need for safe work practices in rapid prototyping laboratories and raised concerns over exposure to novel materials (chemicals), repeated exposure (sensitivity leading to allergic reactions), and potential long-term effects of exposures. Later, Short et al. (2015) performed risk assessments and hazard identification for three AM process categories (ME, BJ, and VP) and identified contact with toxic chemicals (ranging from carcinogens to mucous membrane irritants), use of flammable and explosive materials (e.g. metal dusts), and irradiation of the eyes (UV radiation and lasers) as major potential hazards. Ryan and Hubbard (2016) reported a preliminary hazard assessment for MJ process category. Recently, Petretta et al. (2019) constructed a risk evaluation system for all AM process categories except SL. All AM processes present some form of hazard to workers; however, the potential for exposure varies among the seven categories (Bours et al. 2017; Petretta et al. 2019; Roth et al. 2019), as well as within process phases and the operating environment (Roth et al. 2019). Inhalation of particles (including ultrafine particles) and semi- and volatile organic compound (SVOC, VOC) emissions, dermal exposure to binders, powders, resins, and solvents and UV radiation are now considered to be among the most important health hazards associated with AM (Petretta et al. 2019; Roth et al. 2019). In particular, exposures to ultrafine particles (diameter < 100 nm) pose a challenge for occupational hygienists who are accustomed to mass-based exposure measurements. Ultrafine particles, because of their small size, have little mass and thus characterized in terms of number concentration. Exposure to ultrafine particles was shown to induce adverse cardiovascular effects (e.g., hypertension) in humans and experimental animals. Further, because of their small size, these particles can penetrate to the deepest portion of the lung and translocate to extrapulmonary sites where they can induce toxic effects (Elder and Oberdörster 2006). At this time, there are no particle number-based occupational exposure limits (OELs) so hygienists and toxicologists have no standard against which measurements can be compared to determine if exposures are acceptable or unacceptable. Some investigators characterized FFF 3D printer particle number-based ERs as low (< 10⁹ #/min), medium (10⁹ #/min), and high (> 10⁹ #/min) using criteria developed by He, Morawska, and Taplin (2007) for laser printers; however, these classifications are not related to health risks. Additional hazards of AM include electrical shock, thermal burns, mechanical injury (during maintenance and malfunction), noise, contact with biological agents (e.g., 3D bioprinting), fatigue (long shift durations), psychosocial stress, and repetitive manual tasks (ergonomics/human factors) (Petretta et al. 2019; Roth et al. 2019).

Exposures need to be controlled via the hierarchy of controls, which includes, but is not limited to proper facility and process design, ventilation and dust collection, adequate workspace, and, as a last resort, use of personal protective technologies such as respirators. Examples of effective controls for preventing or reducing exposures were described in the literature (Dunn et al. 2020b; Katz et al. 2020; Pelley 2018; Petretta et al. 2019; Roth et al. 2019).

Methods

The Scopus and PubMed databases were searched in July 2020 using the keywords (additive manufacturing OR 3-d print* OR 3-dimensional) AND (emissions OR exposure), which returned 888 and 416 citations, respectively. Each abstract was reviewed by one author to determine if the citation met the eligibility criteria for this review, i.e., available in English language and reported original data on substances released from an AM process into a workplace or other indoor space that could be occupied by a person (all environmental test chamber studies were excluded). Based upon these criteria, 27 of the 888 citations from Scopus and 12 of the 416 citations from PubMed were retained. These 39 citations were merged, and 8 duplicates were removed, which resulted in 31 candidate articles for detailed review. Next, both databases were searched using variations of AM process category and machine names. For example, for vat photopolymerization, the keywords were (vat printing OR SLA printing OR DLP printing OR LCD printing OR continuous liquid interface production OR low force stereolithography) AND (emissions OR exposure). These search queries identified an additional five citations that met our eligibility criteria and brought the total number of candidate articles to 36. All authors obtained these articles and reviewed them in detail. During this detailed review, an additional 6 articles that met our eligibility criteria were identified from citations in the articles, which raised the total to 42 articles. From the time of the initial literature review to December 31, 2020, four relevant articles were published electronically that were identified using a weekly key word search alert of the Scopus database, bringing the final total to 46 articles that were included in this review. Recently, Leso et al. (2021) reviewed 18 articles specific to workplace exposure assessments and discussed issues related to risk management and exposure mitigation and the reader is referred to that publication for more information on those topics.

AM process category emissions and associated exposures

Since the first publication on particle emissions from ME-type FFF 3-D printers in 2013 (Stephens et al. 2013), the number of articles related to emissions and exposures associated with AM published per year has increased and reached a maximum of 17 in 2019 (Figure 2). With time, studies on the various AM process categories have diversified beyond just the ME process category, with studies of five different AM process categories published in the last two years respectively. AM emissions and exposure articles included in this review originated from 23 countries, which highlights the global impact of this technology and international efforts to ensure that proper health and safety precautions are implemented during use. The USA was responsible or involved in 46% of published articles and France, South Africa, Singapore, and Sweden were responsible or involved in 7% of published articles (Figure 3).

Figure 2. — AM workspace emission and exposure articles published from 2013 to 2020 according to process categories and year of publication.

Figure 3. — AM workspace emission and exposure articles according to countries of origin (drawn on mapchart.net).

For the purposes of this review, the term emission was defined as any substance that was released from an AM process or associated task and the term exposures was defined as the amount of a substance that was measured in a person’s breathing zone, on their skin, or in a biological fluid. Additional details on hazards associated with metallic feedstock used in AM processes have been published (Chen et al. 2020; Sousa, Arezes, and Silva 2019) as were additional details on hazards specific to acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) filaments used in ME processes (Aluri et al. 2021). Literature on particle emissions and exposures are summarized in Tables 2 and 3, respectively. Gas-phase emissions and exposures are summarized in Tables 4 and 5, respectively. Several investigators reported comprehensive measurements for metals and/or VOCs; however, for brevity, only the top five substances by mass concentration from these studies were included in the tables. Emissions and exposures occur throughout the entire AM process, which includes pre-printing tasks (cleaning a build chamber, loading feedstock in a machine, etc.), printing, post-printing tasks (retrieving a printed part, unloading feedstock from a machine, etc.), and post-processing tasks (cleaning, polishing, machining and other manipulations of printed parts, etc.). Data presented herein are useful to occupational (industrial) hygienists for understanding exposure potential and to toxicologists for developing experimental protocols based on real-world data for in vitro and in vivo studies.

Table 2.

Summary of particle-phase releases (emission rates and concentrations) from additive manufacturing machines by process category ( $\bar{X} C_{num}$ = average particle number concentration in #/cm³, ER_num = particle number-based emission rate in #/min, $\bar{X} C_{mass}$ = average particle mass concentration in μg/m³).

Room (m³)	ACH (hr⁻¹)	Feedstock^a	Scenario^b	Sampler^c	Specifics^d	$\bar{X} C_{num}$	ER_num	$\bar{X} C_{mass}$	Cit.^f
Binder jetting AM process category
157	6	Gypsum	Cover shut	CFC (TF)	TSP			400	A
				SMPS	205 nm	9000	4.4 × 10⁴
				SMPS	255 nm	1.2 × 10⁴
				SMPS	<407 nm	1 × 10⁴⁻3 × 10⁴
				OPS	PM₁			680 (P)^e
				OPS	PM_2.5			58
								800 (P)
				OPS	PM₁₀			80
								1100 (P)
70	NR	SS	Printer setup	OPS	0.3 to 10 μm	3.5 × 10⁴			B
			Printing	OPS	0.3 to 10 μm	3.8 × 10⁴
			Depowdering	OPS	0.3 to 10 μm	3.3 × 10⁴
			Printing	SMPS	27 to 65 nm	7000
			1 m to printer	Impactor (TF)	PM_2.5			30
			1 m to printer	CFC (TF)	PNOC			up to 80
			3 m to printer	CFC (TF)	PNOC			20
Directed energy deposition AM process category
NR	NR	316 L SS, Inconel 625	Printing	CNC	10 to 1000 nm	0.5 × 10⁶⁻1.5 × 10⁶			C
		316 L SS	10VX nozzle	Inhal. (PVC)	Fe			124
				Inhal. (PVC)	Cr			43.8
				Inhal. (PVC)	Mn			14.2
				Inhal. (PVC)	Ni			19.5
				Inhal. (PVC)	Mo			6.8
			10VX nozzle	Resp. (PVC)	Fe			61.7
				Resp. (PVC)	Cr			30.9
				Resp. (PVC)	Mn			14.5
				Resp. (PVC)	Ni			8.0
				Resp. (PVC)	Mo			<7.1
		316 L SS	24 VX nozzle	Inhal. (PVC)	Fe			283
				Inhal. (PVC)	Cr			110
				Inhal. (PVC)	Mn			31.6
				Inhal. (PVC)	Ni			42.2
				Inhal. (PVC)	Mo			12.5
				Resp. (PVC)	Fe			196
				Resp. (PVC)	Cr			86.3
				Resp. (PVC)	Mn			28.1
				Resp. (PVC)	Ni			27.7
				Resp. (PVC)	Mo			9.1
		Inconel 625	10VX nozzle	Inhal. (PVC)	Fe			19.6
				Inhal. (PVC)	Cr			86.3
				Inhal. (PVC)	Mn			10.7
				Inhal. (PVC)	Ni			92.2
				Inhal. (PVC)	Mo			9.1
				Resp. (PVC)	Cr			55.1
				Resp. (PVC)	Mn			10.8
				Resp. (PVC)	Ni			70.3
				Resp. (PVC)	Mo			<9.0
		Inconel 625	24 VX nozzle	Inhal. (PVC)	Fe			44.7
				Inhal. (PVC)	Cr			306
				Inhal. (PVC)	Mn			45.0
				Inhal. (PVC)	Ni			456
				Inhal. (PVC)	Mo			77.7
				Resp. (PVC)	Fe			28.0
				Resp. (PVC)	Cr			261
				Resp. (PVC)	Mn			44.6
				Resp. (PVC)	Ni			346
				Resp. (PVC)	Mo			66.4
Material extrusion AM process category
45	NR	PLA	3-DP	SMPS	10 to 116 nm	2.9 × 10⁴	4.0 × 10⁹		D
				SMPS	10 to 100 nm	2.8 × 10⁴	2.0 × 10¹⁰
45	NR	ABS	3-DP	SMPS	10 to 116 nm		4.0 × 10¹⁰
				SMPS	10 to 100 nm		1.9 × 10¹¹
60	NR	ABS	3-DP (n = 1)	OPS	250 to 280 nm	25 (P)			E
			3-DP (n = 2)	OPS	250 to 280 nm	40 (P)
8	0.1	PLA	3-DP T_n = 180 to 220	CNC	2.5 to 1000 nm	0.3 × 10⁵–4.5 × 10⁵ (P)			F
			3-DP R_f = 30 to 90	CNC	2.5 to 1000 nm	5000–5200 (P)
8	0.1	ABS	3-DP T_n = 200 to 240	CNC	2.5 to 1000 nm	0.3 × 10⁵–2.7 × 10⁵ (P)
			3-DP R_f = 30 to 90	CNC	2.5 to 1000 nm	0.7 × 10⁵–2.1 × 10⁵ (P)
28	NR	PLA	3-DP	CNC	20 to 1000 nm	1950		0.014^*	G
544	NR	PLA	3-DP	CNC	20 to 1000 nm	2139		0.015^*
28	NR	PLA	3-DP	CNC	20 to 1000 nm	3534		0.025^*
27	NR	ABS	3-DP	CNC	20 to 1000 nm	1.0 × 10⁵		0.616^*
74	NR	ABS	3-DP	CNC	20 to 1000 nm	2.1 × 10⁴		0.125^*
57	NR	Nylon	3-DP	CNC	20 to 1000 nm	3.8 × 10⁴		0.243^*
34	NR	PC	3-DP	CNC	20 to 1000 nm	1.7 × 10⁵		1.143^*
180	2	PLA	3-DP	EDB/miniDiSC	7 to 400 nm	1700			H
				Resp. (PVC)	D₅₀ = 5 μm			0.7
				Inhal. (CN)	D₅₀ = 100 μm			4.7
30	NR	PLA	3-DP	EDB/miniDiSC	7 to 400 nm	3200
				Resp. (PVC)	D₅₀ = 5 μm			1.6
				Inhal. (CN)	D₅₀ = 100 μm			5.3
40	0.22	PLA	3-DP T_n = 220 to 240	CNC	4 to 1000 nm	0.5 × 10⁴–4.9 × 10⁴ (P)	6.8 × 10⁹–1.0 × 10¹¹		I
40	0.22	PLA Wood-1	3-DP T_n = 220 to 240	CNC	4 to 1000 nm	1.5 × 10⁴–9.3 × 10⁴ (P)	0.6 × 10¹¹⁻2.6 × 10¹¹
40	0.22	PLA Wood-2	3-DP T_n = 230 to 240	CNC	4 to 1000 nm	7.0 × 10⁵–9.5 × 10⁵ (P)	1.9 × 10¹²⁻2.8 × 10¹²
40	0.22	PLA Copper	3-DP T_n = 220 to 240	CNC	4 to 1000 nm	3.6 × 10⁵–6.7 × 10⁵ (P)	1.4 × 10¹²⁻2.0 × 10¹²
40	0.22	PLA Bamboo	3-DP T_n = 210 to 240	CNC	4 to 1000 nm	0.3 × 10⁵–9.5 × 10⁵ (P)	1.7 × 10¹⁰⁻2.7 × 10¹²
40	0.22	Flex PLA	3-DP T_n = 240	CNC	4 to 1000 nm	2.4 × 10⁴ (P)	4.2 × 10¹⁰
40	0.22	CP	3-DP T_n = 220 to 240	CNC	4 to 1000 nm	0.9 × 10⁵–5.6 × 10⁵ (P)	0.2 × 10¹²⁻1.6 × 10¹²
40	0.22	CP-CF	3-DP T_n = 220 to 240	CNC	4 to 1000 nm	1.1 × 10⁵–4.8 × 10⁵ (P)	0.2 × 10¹²–1.2 × 10¹²
40	0.22	Nylon	3-DP T_n = 230 to 240	CNC	4 to 1000 nm	1.3 × 10⁴–1.4 × 10⁴ (P)	1.4 × 10¹¹–1.6 × 10¹¹
40	0.22	Ninja Flex^®	3-DP T_n = 230 to 240	CNC	4 to 1000 nm	1.8 × 10⁴–5.8 × 10⁴ (P)	0.7 × 10¹¹–1.4 × 10¹¹
33	0.3	ABS	3-DP Cover on	SMPS	10 to 420 nm	5.0 × 10⁴ (P)			J
			3-DP Cover off	SMPS	10 to 420 nm	1.9 × 10⁵ (P)
NR	NR	PLA	3-DP (n = 3)	CNC	20 to 1000 nm	3.9 × 10⁴			K
			3-DP (n = 4)	CNC	20 to 1000 nm	5.3 × 10⁴
			3-DP (n = 5)	CNC	20 to 1000 nm	8.7 × 10⁴
NR	NR	ABS	3-DP	SMPS	10 to 420 nm	≈ 4.0 × 10⁵ (P)			L
81	5	PLA	3-DP T_n = 200	CNC	10 to 1000 nm	740	6.0 × 10⁸		M
			3-DP T_n = 230	SMPS	Varied^‡	3.7 × 10⁵	3.1 × 10¹¹
81	5	ABS	3-DP T_n = 230 to 238	SMPS	Varied^‡	0.03–2.8 × 10⁶	2.2 × 10¹⁰–2.3 × 10¹²
			3-DP T_n = 250	SMPS	Varied^‡	1.5 × 10⁶	1.3 × 10¹²
			3-DP Malfunction	SMPS	Varied^‡	4.4 × 10⁵	3.7 × 10¹¹
600	20	PLA	3-DP	CNC	10 to 1000 nm	3000			N
162	1.8	ABS	3-DP	SMPS	2 to 300 nm	3780		0.001^*
777	NR	ABS	3-DP	CNC	15 to 1000 nm	3900 (P)			0
36	NR	ABS	3-DP	SMPS	10 to 420 nm		10³–10⁵
141	NR	ABS	3-DP	CNC	15 to 1000 nm	6.6 × 10⁴ (P)
66	NR	ABS, PC, Ultem^®	FDM^™ Opening doors	CNC	7 to 1000 nm	600–800			P
40	NR	ABS, PLA	3-DP Cover off	CNC	7 to 1000 nm	0.5–2.0 × 10⁵
NR	NR	ABS	3-DP Inside machine	SMPS	16 to 583 nm	6.8 × 10⁵ (P)	1.1 × 10⁹		Q
NR	NR	ASA	3-DP Inside machine	SMPS	16 to 583 nm	1.2 × 10⁶ (P)	5.9 × 10⁹
NR	NR	PLA/PU Support	3-DP Inside machine	SMPS	16 to 583 nm	2.0 × 10⁴ (P)	7.2 × 10⁵
NR	NR	CP	3-DP Inside machine	SMPS	16 to 583 nm	7.9 × 10⁵ (P)	3.3 × 10⁵
NR	NR	Nylon	3-DP Inside machine	SMPS	16 to 583 nm	2.1 × 10⁶ (P)	3.5 × 10⁹
NR	NR	PC	3-DP Inside machine	SMPS	16 to 583 nm	1.1 × 10⁶ (P)	1.8 × 10⁹
NR	NR	PLA Green	3-DP Inside machine	SMPS	16 to 583 nm	2.5 × 10³ (P)	1.1 × 10⁶
NR	NR	PLA True green	3-DP Inside machine	SMPS	16 to 583 nm	1.3 × 10³ (P)	8.2 × 10⁵
NR	NR	PLA Silver	3-DP Inside machine	SMPS	16 to 583 nm	1.8 × 10³ (P)	3.8 × 10⁵
NR	NR	PLA PolyWood^™	3-DP Inside machine	SMPS	16 to 583 nm	5.6 × 10³ (P)	1.5 × 10⁵
NR	NR	PVA	3-DP Inside machine	SMPS	16 to 583 nm	1.2 × 10⁴	3.3 × 10⁵
NR	NR	TPU	3-DP Inside machine	SMPS	16 to 583 nm	4.0 × 10³	8.4 × 10⁵
66	NR	ABS, PC	FDM^™	CNC	10 to 1000 nm		2.2 × 10¹¹		R
				OPS	0.3 to 20 μm		2.7 × 10⁵
66	NR	Ultem^®	FDM^™	CNC	10 to 1000 nm		4.1 × 10¹⁰
				OPS	0.3 to 20 μm		9.6 × 10⁴
40	NR	ABS, PLA	3-DP (n = 7)	CNC	20 to 1000 nm		9.7 × 10¹⁰		S
76	NR	ABS	3-DP	CNC	20 to 1000 nm		7.3 × 10¹⁰
466	2	PLA	Sheer 3-DP	CNC	20 to 1000 nm		1.9 × 10⁹–3.8 × 10⁹
			Sheer 3-DP Malfunction	CNC	20 to 1000 nm		2.1 × 10¹¹
			Sheer 3-DP	OPS	0.3 to 20 μm		1.0 × 10⁵
			Sheer 3-DP Malfunction	OPS	0.3 to 20 μm		1.0 × 10⁵
			Sheer 3-DP	FMPS	6 to 560 nm		3.0 × 10¹¹
			Sheer 3-DP Malfunction	FMPS	6 to 560 nm		7.4 × 10¹⁰
320	NR	PLA	3-DP	CNC	20 to 1000 nm		0.6 × 10¹⁰–9.0 × 10¹⁰
45	NR	PLA	3-DP	CNC	20 to 1000 nm		1.7 × 10¹¹–4.4 × 10¹¹
195	NR	PLA Wood	3-DP	CNC	20 to 1000 nm	6520			T
			3D-P Malfunction	CNC	20 to 1000 nm	4.2 × 10⁵
			3D-P	LSP	0.1 to 15 μm			10
195	NR	PLA-CF	3D-P	CNC	20 to 1000 nm	2070
				LSP	0.1 to 15 μm			10
195	NR	ABS-FR	3D-P	CNC	20 to 1000 nm	8.2 × 10⁴
				LSP	0.1 to 15 μm			10
NR	1.8	ABS	3-DP Inside machine	CNC	10 to 1000 nm	7.1 × 10⁴			U
				SMPS	2 to 300 nm			7.6^*
14	NR	PLA	3D-P (n = 1)	CFC (PVC)	TSP			300	V
			3D-P (n = 3)	CFC (PVC)	TSP			700
			3D-P (n = 1)	Cyclone (PVC)	D₅₀ = 4 μm			800
			3D-P (n = 3)	Cyclone (PVC)	D₅₀ = 4 μm			400
			3D-P (n = 1)	SMPS	10 to 420 nm	2303–9806
			3D-P (n = 3)	SMPS	10 to 420 nm	9866
						2.2 × 10⁴ (P)
303	29	PEEK	3D-P Cutting part	SMPS	10 to 420 nm	≈ 1.5 × 10⁵ (P)			W
153	NR	PLA	3D-P (n = 20) No LEV	SMPS	10 to 420 nm	4366–6606			X
46	1.9	ABS	3D-P (n = 2)^† No HEPA filter	AMS	30 to 1000 nm			219	Y
				SMPS	15 to 685 nm		4.8 × 10¹⁰
46	4.0	ABS	3D-P (n = 3)^† No HEPA filter	AMS	30 to 1000 nm			56
				SMPS	15 to 685 nm		1.4 × 10¹⁰
46	3.2	PLA	3D-P (n = 3)^† No HEPA filter	AMS	30 to 1000 nm			40
				SMPS	15 to 685 nm		1.2 × 10⁹
355	6.3	ABS	3D-P	CNC	20 to 1000 nm	1.2 × 10⁴	2.8 × 10¹⁰		Z
65	NR	nHA	3-DP Room	miniDiSC	7 to 400	495			GG
			3-DP Room	miniDiSC	7 to 400	404
Material jetting AM process category
NR	NR	VeroWhite Plus RGD835	Inside machine	LSP	PM₁			30	AA
			Room air	LSP	PM_2.5			70
				LSP	PM₁₀			3
48	NR	VisiJet M2R-CL	Room air	LSP	Inhalable			10	T
90	0.22 estimated	TangoBlack+, VeroClear	Lid open	CNC	20 to 1000 nm		2.3 × 10¹⁰		R
				OPS	0.3 to 20 μm
							(1)
							× 10⁵
466	2	TangoBlack+, VeroClear, VeroWhite+	Lid closed	CNC	20 to 1000 nm		1.5 × 10⁹–5.5 × 10⁹
				OPS	0.3 to 20 μm		0.9 × 10⁴–1.1 × 10⁴
				FMPS	5.6 to 560 nm		0.2 × 10¹²–2.1 × 10¹²
Powder bed fusion AM process category
NR	NR	Inconel 939	Cleaning	DC	10 to 300 nm	≈ 1.6 × 10⁴ (P)			BB
			Pre-/post-printing tasks	OPS	0.3 to 10 μm	≈ 5–30 (P)		0.5 × 10⁴–4.0 × 10⁴ (P)
			Near printer 1	CFC (MCE)	Cr			50
				CFC (MCE)	Co			42
				CFC (MCE)	Ni			110
				CFC (MCE)	Mn			0.19
			Near strainer 1	CFC (MCE)	Co			20
				CFC (MCE)	Ni			53
				CFC (MCE)	Mn			0.22
			Near printer 2	CFC (MCE)	Cr			21
				CFC (MCE)	Co			13
				CFC (MCE)	Ni			48
				CFC (MCE)	Mn			0.16
				CFC (MCE)	Mo			2.9
			Near strainer 2	CFC (MCE)	Cr			32
				CFC (MCE)	Co			21
				CFC (MCE)	Ni			71
				CFC (MCE)	Mn			0.18
				CFC (MCE)	Mo			3.2
1176	NR	Nylon-12 Glass filler	Printing	CNC	< 1000 nm	1.7 × 10⁴			T
				LSP	0.1 to 15 μm			40
			Post-printing/processing	LSP	0.1 to 15 μm			400
991	NR	Nylon-12 Glass filler	MJF printing	CNC	< 1000 nm	1110
				LSP	0.1 to 15 μm			50
			Post-printing/processing	LSP	0.1 to 15 μm			190
117	NR	Nylon-12	Pre-printing Virgin powder	LSP	0.1 to 15 μm			523	CC
			Pre-printing Recyc. powder	LSP	0.1 to 15 μm			706
			Printing Virgin powder	LSP	0.1 to 15 μm			39
			Printing Recyc. powder	LSP	0.1 to 15 μm			46
			Post-printing Virgin powder	LSP	0.1 to 15 μm			46
			Post-printing Recyc. powder	LSP	0.1 to 15 μm			95
NR	NR	316 L SS	Oper. station Day 1	NSAM	10 to 487 nm	457			DD
			Oper. station Day 2	NSAM	10 to 487 nm	294
			Oper. station Day 3	NSAM	10 to 487 nm	379
			Oper. station Day 1	SMPS	10 to 420 nm	1.8 × 10⁴
			Oper. station Day 2	SMPS	10 to 420 nm	1.2 × 10⁴
			Oper. station Day 3	SMPS	10 to 420 nm	1.5 × 10⁴
			Machine rear Day 1	SMPS	10 to 420 nm	6021
			Machine rear Day 2	SMPS	10 to 420 nm	5262
			Machine rear Day 3	SMPS	10 to 420 nm	6384
			Feeding silos Day 1	SMPS	10 to 420 nm	6382
			Feeding silos Day 2	SMPS	10 to 420 nm	5610
			Feeding silos Day 3	SMPS	10 to 420 nm	6774
NR	NR	304 L SS	NR	DC	10 to 300 nm	6300			EE
148	9.3	Nylon-12	Printing	CNC	20 to 1000 nm	1.5 × 10⁴	2.8 × 10¹⁰		Z
			Phase I	LSP	0.1 to 15 μm			110–450
			Phase II	LSP	0.1 to 15 μm			510–1790
			Pouring	LSP	0.1 to 15 μm			1.5 × 10⁵
NR	NR	Ti6Al4V	Emptying @ FF	CNC	10 to 1000 nm	1.5 × 10³			FF
			Opening PRS, Cleaning @ FF	CNC	10 to 1000 nm	2.5 × 10³
			Grinding @ FF	CNC	10 to 1000 nm	1.5 × 10⁴
			Grinding @ NF	CNC	10 to 1000 nm	2.5 × 10⁵
			Printing @ NF	LSP	Respirable			58.4
			Printing @ NF	Cyclone (TF)	Respirable			50.4
Vat photopolymerization AM process category
55	NR	VarseoWax	Scenario 1 Outside machine <1 m (printing)	CNC	20 to 1000 nm	8020			T
				LSP	Inhalable			50

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ABS = acrylonitrile butadiene styrene, ASA = acrylonitrile styrene acrylate, CF = carbon fiber additive, CP = co-polyester, FR = flame retardant additive, nHA = nanoscale hydroxyapatite in unspecified polymer matrix, PC = polycarbonate, PEEK = poly ether ether ketone, PLA = polylactic acid, PU = polyurethane, PVA = polyvinyl alcohol, SS = stainless steel, TPU = thermoplastic polyurethane

3-DP = desktop-scale fused filament fabrication 3D printer, FDM^™ = industrial-scale fused deposition modeling machine, FF = far-field, HEPA = high-efficiency particulate air filter, LEV = local exhaust ventilation, MJF = multi-jet fusion machine, NF = near-field, PRS = powder removal system, R_f = filament feed rate (mm/s), T_n = extruder nozzle temperature (°C)

AMS = aerosol mass spectrometer, CFC = close-faced cassette, CN = cellulose nitrate filter, CNC = condensation nuclei counter, DC = diffusion charger, EDB = electrometer-based diffusion battery, FMPS = fast mobility particle sizer, Respirable = respirable sampler (e.g., FSP-10 cyclone or GK2.69 cyclone), Inhal. = inhalable sampler (e.g., Button, GSP-10, or Institute of Occupational Medicine [IOM] sampler), LSP = light scattering photometer (e.g., DustTrak^™ or environmental particulate air monitor), NSAM = nanoparticle surface area monitor, MCE = mixed cellulose ester filter, OPS = optical particle sizer, PVC = polyvinyl chloride filter, Resp. = respirable sampler (e.g., nylon, aluminum, or FSP10 cyclone), SMPS = scanning mobility particle sizer, TF = Teflon^® (polytetrafluoroethylene) filter

Co = cobalt, Cr = chromium, D₅₀ = 50% aerodynamic particle diameter cutoff, Fe = iron, Mn = manganese, Mo = molybdenum, Ni = nickel, PM_x = particulate matter with aerodynamic diameter less than 1 μm, 2.5 μm, or 10 μm, PNOC = particulate not otherwise classified, TSP = total suspended particulate

P = peak

A = Afshar-Mohajer et al. (2015), B = Lewinski, Secondo, and Ferri (2019), C = Bau et al. (2020), D = Stephens et al. (2013), E = Zhou et al. (2015), F = Deng et al. (2016), G = McDonnell et al. (2016), H = Steinle (2016), I = Stabile et al. (2017), J = Yi et al. (2016), K = Bharti and Singh (2017), L = Simon, Aguilera, and Zhao (2017), M = Mendes et al. (2017), N = Zontek et al. (2017), O = Vance et al. (2017), P = Du Preez et al. (2018b), Q = Chýlek et al. (2019), R = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Martin, et al. (2019b), S = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Menchaca, et al. (2019c), T = Väisänen et al. (2019), U = Zontek et al. (2019), V = Chan et al. (2020), W = Dunn, Dunn, et al. (2020a), X = Dunn, Hammond, et al. (2020b), Y = Katz et al. (2020), Z = Zisook et al. (2020), AA = Ryan and Hubbard (2016), BB = Graff et al. (2017), CC = Damanhuri, Subki, et al. (2019b), DD = Gomes et al. (2019), EE = Ljunggren et al. (2019), FF = Jensen et al. (2020), GG = Oberbek et al. (2019)

Calculated by study authors assuming spherical particle shape and density of polymer

^‡

Authors report using one brand of SMPS at different inlet flows corresponding to size ranges of 2 to 65 nm and 4.5 to 141 nm and another brand of SMPS with size range 5.5 to 350 nm, but report results as “SMPS”

^†

50^th percentile value reported for all printers in a scenario was divided by number of printers in use to obtain unit specific emission rates

NR = not reported

Table 3.

Summary of particle-phase personal breathing zone exposures among additive manufacturing workers.

Room (m³)	ACH (h⁻¹)	Feedstock^a	Scenario^b	Sampler^c	Specifics	Analysis^d	Analyte^e	C (μg/m³)	Cit.^f
Directed energy deposition AM process category
NR	NR	316 L SS	End of build	miniDiSC	Real-time	n/a	Particles	5.0 × 10⁶ ^#	A
Material extrusion AM process category
66	NR	ABS, PLA Employee 1	3-DP	NRD	10 to 300 nm	ICP-MS	Al	10	B
40	NR	ABS, PLA Employee 1	3-DP/AVP	NRD	10 to 300 nm	ICP-MS	Al	20
40	NR	ABS, PLA Employee 2	3-DP/AVP	NRD	10 to 300 nm	ICP-MS	Fe	10
66	NR	ABS, PC	FDM^™	NRD	10 to 300 nm	ICP-MS	Al	Up to 10	C
				NRD	10 to 300 nm	ICP-MS	Fe	Up to 10
40	NR	ABS, PLA	3-DP	NRD	10 to 300 nm	ICP-MS	Al	10–20	D
76	NR	ABS	3-DP	NRD	10 to 300 nm	ICP-MS	Al	10–20
303	29	PEEK CNF/CNT	3-DP	OFC (MCE)	Total	TEM	CNF/CNT	Present^*	E
Material jetting AM process category
90	0.22 estimated	TangoBlack+, VeroClear	Printing	NRD	10 to 300 nm	ICP-MS	Al	Up to 10	C
		TangoBlack+, VeroClear		NRD	10 to 300 nm	ICP-MS	Fe	Up to 10
Powder bed fusion AM process category
NR	NR	Inconel 939	Pre-/printing tasks	CFC (MCE)	Total	ICP-MS	Cr	44	F
				CFC (MCE)	Total	ICP-MS	Co	38
				CFC (MCE)	Total	ICP-MS	Ni	99
				CFC (MCE)	Total	ICP-MS	Mn	0.17
NR	NR	Inconel 718, Ti64	Pre-/post-printing tasks	Cyclone (CN)	Inhalable	GF-AAS	Ni	12.5	G
				Cyclone (CN)	Inhalable	GF-AAS	Cr	3.5
				Cyclone (CN)	Inhalable	ICP-MS	Fe	10
				Cyclone (CN)	Inhalable	GF-AAS	Ti	11.5
				Cyclone (CN)	Inhalable	FAAS	Al	104
				Cyclone (CN)	Respirable	GF-AAS	Ni	0.6
				Cyclone (CN)	Respirable	GF-AAS	Ti	1.6
NR	NR	304 L SS	Printing – Year 1	IOM (MCE)	Inhalable	ICP-MS	Cr	6.8–86.8	H
				IOM (MCE)	Inhalable	ICP-MS	Fe	114.7–253.8
				IOM (MCE)	Inhalable	ICP-MS	Ni	6.6–268.9
			Printing – Year 2	IOM (MCE)	Inhalable	ICP-MS	Cr	3.0–331.0
				IOM (MCE)	Inhalable	ICP-MS	Fe	23.9–283.3
				IOM (MCE)	Inhalable	ICP-MS	Ni	5.1–715.7
			Printing – Year 1	OFC (MCE)	Total dust	ICP-MS	Cr	2.0–59.4
				OFC (MCE)	Total dust	ICP-MS	Fe	100.8–253.8
				OFC (MCE)	Total dust	ICP-MS	Ni	2.0–256.1
NR	NR	Ti6Al4V	Emptying print chamber	miniDiSC	Real-time	n/a	Particles	4.2 × 10³	I
			PRS closed	miniDiSC	Real-time	n/a	Particles	0.6 × 10³
			PRS open	miniDiSC	Real-time	n/a	Particles	1.5 × 10³
			Baking	miniDiSC	Real-time	n/a	Particles	1.0 × 10³
			Grinding	miniDiSC	Real-time	n/a	Particles	3.6 × 10⁴

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ABS = acrylonitrile butadiene styrene, CNF = carbon nanofiber, CNT = carbon nanotube, PC = polycarbonate, PEEK = poly ether ether ketone, PLA = polylactic acid, SS = stainless steel

3-DP = desktop-scale fused filament fabrication 3-D printer, AVP = acetone vapor polishing post-processing task, FDM^™ = industrial-scale fused deposition modeling machine, PRS = powder removal system

CFC = close-faced cassette, CN = cellulose nitrate filter, MCE = mixed cellulose ester filter, OFC = open-faced cassette, NRD = nanoparticle respiratory deposition sampler

FAAS = flame atomic absorption spectrometry, GF-AAS = graphite furnace-atomic absorption spectrometry, ICP-MS = inductively coupled plasma-mass spectrometry, TEM = transmission electron microscopy

Al = aluminum, CNF = carbon nanofiber, CNT = carbon nanotube, Co = cobalt, Cr = chromium, Fe = iron, Mn = manganese, Ni = nickel, Ti = titanium

A = Bau et al. (2020), B = Du Preez et al. (2018b), C = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Martin, et al. (2019b), D = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Menchaca, et al. (2019c), E = Dunn, Dunn, et al. (2020), F = Graff et al. (2017), G = Walter et al. (2018), H = Ljunggren et al. (2019), I = Jensen et al. (2020)

^{# =}

number concentration (#/cm³)

Free CNT and polymer particles that contained CNF/CNT

NR = not reported

Table 4.

Summary of gas-phase releases (emission rates and concentrations) from additive manufacturing machines by process type.

Room (m³)	ACH (hr⁻¹)	Feedstock^a	Scenario^b	Sampler^c	Specifics^d	Analysis^e	Analyte^f	$\bar{X} C (μ g / m^{3})$ ^g	ER (mg/min)	Cit.^h
Binder jetting AM process category
157	6	Gypsum	Cover shut	PID	10.6 eV	n/a	TVOC	1725 (P)	22–27	A
Material extrusion AM process category
28	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC	102 480 (P)		B
544	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC	408 734 (P)
28	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC	578 1010 (P)
27	NR	ABS	3-DP	PID	10.6 eV	n/a	TVOC	186 333 (P)
74	NR	ABS	3-DP	PID	10.6 eV	n/a	TVOC	172 365 (P)
57	NR	Nylon	3-DP	PID	10.6 eV	n/a	TVOC	2570 3534 (P)
34	NR	PC	3-DP	PID	10.6 eV	n/a	TVOC	895 6504 (P)
180	2	PLA	3-DP	PID	10.6 eV	n/a	TVOC	33–38		C
				TD Tube	Tenax^®	GC-MS	MM	0.7
30	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC	92–216
			3-DP	TD Tube	Tenax^®	GC-MS	MM	5.5–19
81	5	ABS, PLA	3-DP	Cartridge	Silica gel	LC-MS	Formaldehyde	2–3		D
40	NR	ABS	AVP	TD tube	SVI	GC-MS	Acetone	100		E
				PID	10.6 eV	n/a	TVOC	9.0 × 10⁵
40	NR	PLA	CVP Pouring CHCl₃	PID	10.6 eV	n/a	TVOC	2.4 × 10⁵
			CVP Brushing CHCl₃	PID	10.6 eV	n/a	TVOC	1.0 × 10⁵–2.0 × 10⁵
66	NR	ABS, PC	FDM^™	PID	10.6 eV	n/a	TVOC		19	F
				Gas sensor	SC	n/a	Ozone	37
66	NR	ABS, PC Morning	FDM^™	TD tube	SVI	GC-MS	Acetone	0.6 × 10⁴–3.3 × 10⁴
66	NR	ABS, PC Afternoon	FDM^™	TD tube	SVI	GC-MS	Acetone	0.3 × 10⁴–1.6 × 10⁴
66	NR	Ultem^®	FDM^™	PID	10.6 eV	n/a	TVOC		94
				Gas sensor	SC	n/a	Ozone	43
				TD tube	SVI	GC-MS	Acetone	400
40	NR	ABS, PLA	3-DP (n = 7)	PID	10.6 eV	n/a	TVOC		3300	G
				TD tube	SVI	GC-MS	Acetone	98.7
				TD tube	SVI	GC-MS	IPA	122.2
76	NR	ABS	3-DP	PID	10.6 eV	n/a	TVOC		120
				TD tube	SVI	GC-MS	Acetone	457
				TD tube	SVI	GC-MS	Benzene	8.2
				TD tube	SVI	GC-MS	Hexane	7.7
				TD tube	SVI	GC-MS	IPA	4637
466	2	PLA	Sheer 3-DP	PID	10.6 eV	n/a	TVOC		16–31
			Sheer 3-DP Malfunction	PID	10.6 eV	n/a	TVOC		23
320	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC		2–44
45	NR	PLA	3-DP	PID	10.6 eV	n/a	TVOC		8–11
				TD tube	SVI	GC-MS	Acetaldehyde	43.0–43.1
				TD tube	SVI	GC-MS	Acetone	222–273
				TD tube	SVI	GC-MS	IPA	2.3 × 10⁴–4.1 × 10⁴
				TD tube	SVI	GC-MS	MC	6.3–9.2
195	NR	PLA EasyWood^™	3-DP	TD Tube	Tenax^® TA	GC-MS	Decanal	8		H
				TD Tube	Tenax^® TA	GC-MS	DCPS	8
				TD Tube	Tenax^® TA	GC-MS	BEA	16
				TD Tube	Tenax^® TA	GC-MS	PG	17
				TD Tube	Tenax^® TA	GC-MS	TVOC (ΣVOC_i)	117
				Sorbent tube	DNPH	HPLC-UV	Formaldehyde	11
				Sorbent tube	DNPH	HPLC-UV	Acetone	17
				Sorbent tube	DNPH	HPLC-UV	Butanone	15
195	NR	PLA-CF	3-DP	TD Tube	Tenax^® TA	GC-MS	DCPS	11
				TD Tube	Tenax^® TA	GC-MS	Decanal	15
				TD Tube	Tenax^® TA	GC-MS	BEA	44
				TD Tube	Tenax^® TA	GC-MS	Benzoic acid	47
				TD Tube	Tenax^® TA	GC-MS	TVOC (ΣVOC_i)	180
				Sorbent tube	DNPH	HPLC-UV	Formaldehyde	14
				Sorbent tube	DNPH	HPLC-UV	Acetone	20
				Sorbent tube	DNPH	HPLC-UV	Butanone	14
195	NR	ABS-FR	3-DP	TD Tube	Tenax^® TA	GC-MS	Decanal	23
				TD Tube	Tenax^® TA	GC-MS	NDEE	23
				TD Tube	Tenax^® TA	GC-MS	BEA	26
				TD Tube	Tenax^® TA	GC-MS	I. Myristate	34
				TD Tube	Tenax^® TA	GC-MS	TVOC (ΣVOC_i)	338
195	NR	ABS-FR	3-DP	Sorbent tube	DNPH	HPLC-UV	Formaldehyde	18
				Sorbent tube	DNPH	HPLC-UV	Acetaldehyde	8
				Sorbent tube	DNPH	HPLC-UV	Acetone	74
				Sorbent tube	DNPH	HPLC-UV	Butanone	8
NR	NR	ABS	3-DP Inside machine	Sorbent tube	Charcoal	GC-MS	Toluene	16		I
				Sorbent tube	Charcoal	GC-MS	Styrene	69
				Sorbent tube	Charcoal	GC-MS	TVOC	391
NR	NR	PLA	3-DP Inside machine	Sorbent tube	Charcoal	GC-MS	Toluene	26
				Sorbent tube	Charcoal	GC-MS	Styrene	21
				Sorbent tube	Charcoal	GC-MS	TVOC	255
NR	NR	PET	3-DP Inside machine	Sorbent tube	Charcoal	GC-MS	Toluene	11
				Sorbent tube	Charcoal	GC-MS	Styrene	6
				Sorbent tube	Charcoal	GC-MS	TVOC	151
126	NR	PLA	3-DP (n = 5)	TD Tube	Tenax^® TA	GC-MS	Acrylonitrile	7.3		J
				TD Tube	Tenax^® TA	GC-MS	MC	5.7
				TD Tube	Tenax^® TA	GC-MS	Hexane	29.8
				TD Tube	Tenax^® TA	GC-MS	Toluene	6.2
				TD Tube	Tenax^® TA	GC-MS	Xylenes	5.6
14	NR	PLA	3-DP (n = 1)	Sorbent tube	DNPH	HPLC-UV	Formaldehyde	4.9		K
				TD Tube	Sorbent	GC-MS	IPA	190
				TD Tube	Sorbent	GC-MS	Acetone	10
				TD Tube	Sorbent	GC-MS	TVOC	270
14	NR	PLA	3-DP (n = 3)	Sorbent tube	DNPH	HPLC-UV	Formaldehyde	4.5
				TD Tube	Sorbent	GC-MS	IPA	1400
				TD Tube	Sorbent	GC-MS	Acetone	110
				TD Tube	Sorbent	GC-MS	Ethanol	77
				TD Tube	Sorbent	GC-MS	TVOC	1700
355	6.3	ABS	3D-P	Minican	Si-lined	GC-MS	IPA	2260		L
NR	NR	ABS	3D-P Inside machine	OE nose	Dye-based	Digital	Cyclohexanone	Present		M
							Ethyl benzene	Present
							Isobutanol	Present
							Styrene	Present
		PLA	3D-P Inside machine	OE nose	Dye-based	Digital	Acetone
							Isobutanol	Present
							Lactide	Present
							MM	Present
		PETG	3D-P Inside machine	OE nose	Dye-based	Digital	Acetone	Present
							Formaldehyde	Present
							Toluene	Present
Material jetting AM process category
48	NR	VisiJet M2R-CL	Printing	TD Tube	Tenax^®	GC-MS	Iso. acrylate	1325–2076		H
				TD Tube	Tenax^®	GC-MS	2-Furn.	127–164
				TD Tube	Tenax^®	GC-MS	BHT	61–113
				TD Tube	Tenax^®	GC-MS	o-Xylene	64–102
				TD Tube	Tenax^®	GC-MS	TVOC	2001–2872
			Post-processing	TD Tube	Tenax^®	GC-MS	Iso. acrylate	1233
				TD Tube	Tenax^®	GC-MS	BHT	225
				TD Tube	Tenax^®	GC-MS	2-Furan.	112
				TD Tube	Tenax^®	GC-MS	m,p-Xylene	76
				TD Tube	Tenax^®	GC-MS	TVOC	1809
90	0.22 estimated	TangoBlack+, VeroClear	Lid open	PID	10.6 eV	n/a	TVOC		2.8 × 10⁴	F
				TD tube	SVI	GC-MS	Acetaldehyde	54
				TD tube	SVI	GC-MS	Ethanol	1.1 × 10⁴
				Gas sampler	SC	n/a	Ozone	26.3
466	2	TangoBlack+, VeroClear, VeroWhite+	Lid closed	PID	10.6 eV	n/a	TVOC		2.5 × 10⁴–4.5 × 10⁴
				TD tube	SVI	GC-Ms	Acetaldehyde	14–214
				Canister	Evacuated	GC-MS	Ethanol	70.6
				Canister	Evacuated	GC-MS	IPA	149–342
				Canister	Evacuated	GC-MS	MM	4.4
				Gas sensor	SC	n/a	Ozone	9–11
Powder bed fusion AM process category
1176	NR	Nylon-12 Glass filler	Printing	TD Tube	Tenax^®	GC-MS	Siloxanes	27		H
				TD Tube	Tenax^®	GC-MS	TVOC	113
				TD Tube	Tenax^®	GC-MS	Formaldehyde	40
				TD Tube	Tenax^®	GC-MS	Acetaldehyde	42
				IAQ-Calc^™	NDIR	n/a	CO₂	450 ppm
				IAQ-Calc^™	EC	n/a	CO	0.1 ppm
991	NR	Nylon-12 Glass filler	MJF	TD Tube	Tenax^®	GC-MS	Alcohols	223
				TD Tube	Tenax^®	GC-MS	Aliphatic hydrocarbons	59
				TD Tube	Tenax^®	GC-MS	Aromatic hydrocarbons	161
				TD Tube	Tenax^®	GC-MS	TVOC	1114
				TD Tube	Tenax^®	GC-MS	Acetone	41
				IAQ-Calc^™	NDIR	n/a	CO₂	680 ppm
				IAQ-Calc^™	EC	n/a	CO	0.4 ppm
117	NR	Nylon-12	Pre-printing Virgin powder	PID	10.6 eV	n/a	TVOC	872		N
			Pre-printing Recyc. powder	PID	10.6 eV	n/a	TVOC	620
			Printing Virgin powder	PID	10.6 eV	n/a	TVOC	528
			Printing Recyc. powder	PID	10.6 eV	n/a	TVOC	1285
			Post-printing Virgin powder	PID	10.6 eV	n/a	TVOC	803
			Post-printing Recyc. powder	PID	10.6 eV	n/a	TVOC	2410
		Nylon-12	Pre-printing Virgin powder	Gas sensor	NDIR	n/a	CO₂	954 ppm
			Pre-printing Recyc. powder	Gas sensor	NDIR	n/a	CO₂	914 ppm
			Printing Virgin powder	Gas sensor	NDIR	n/a	CO₂	613 ppm
			Printing Recyc. powder	Gas sensor	NDIR	n/a	CO₂	577 ppm
			Post-printing Virgin powder	Gas sensor	NDIR	n/a	CO₂	757 ppm
			Post-printing Recyc. powder	Gas sensor	NDIR	n/a	CO₂	869 ppm
117	NR	Nylon-12	Pre-printing	PID	10.6 eV	n/a	TVOC	872		O
			Printing	PID	10.6 eV	n/a	TVOC	544
			Post-printing	PID	10.6 eV	n/a	TVOC	817
			Pre-printing	Gas sensor	EC	n/a	Formaldehyde	49
			Printing	Gas sensor	EC	n/a	Formaldehyde	32
			Post-printing	Gas sensor	EC	n/a	Formaldehyde	45
117	NR	Nylon-12	Printing	Canister	Evacuated	GC-MS	IPA	442		L
				Canister	Evacuated	GC-MS	Propylene	45
Vat photopolymerization AM process category
NR	NR	Resin	Drilling parts	Badge	Passive	GC-MS	IPA	590		P
55	NR	VarseoWax	Scenario 1 Outside machine <1 m (printing)	TD Tube	Tenax^®	GC-MS	THF alcohol	18		H
				TD Tube	Tenax^®	GC-MS	p-Xylene	13–16
				TD Tube	Tenax^®	GC-MS	MM	136
				TD Tube	Tenax^®	GC-MS	2-BAME	55–63
				TD Tube	Tenax^®	GC-MS	4-M-2-P	3–76
				TD Tube	Tenax^®	GC-MS	TVOC	182–427
				Sorbent tube	DNPH	HPLC-UV	Formaldehyde	12
				Sorbent tube	DNPH	HPLC-UV	Acetone	136
				IAQ-Calc^™	NDIR	n/a	CO₂	550–860 ppm
				IAQ-Calc^™	EC	n/a	CO	0–1.8 ppm
			Part washing	TD Tube	Tenax^®	GC-MS	Ethanol	139
				TD Tube	Tenax^®	GC-MS	IPA	1658
				TD Tube	Tenax^®	GC-MS	TFP	442
				TD Tube	Tenax^®	GC-MS	MM	292
				TD Tube	Tenax^®	GC-MS	4-M-2-P	8139
				TD Tube	Tenax^®	GC-MS	TVOC	11084
155	NR	Grey & Castable resins	Scenario 2 Outside machine <1 m (printing)	TD Tube	Tenax^®	GC-MS	IPA	8–24
				TD Tube	Tenax^®	GC-MS	Acetic acid	28
				TD Tube	Tenax^®	GC-MS	MM	35–93
				TD Tube	Tenax^®	GC-MS	EM	14–34
				TD Tube	Tenax^®	GC-MS	TVOC	84–176
				Sorbent tube	DNPH	HPLC-UV	Acetone	17
				Sorbent tube	DNPH	HPLC-UV	Butanone	22
				IAQ-Calc^™	NDIR	n/a	CO₂	470–650 ppm
NR	NR	White resin	Drilling models	Badge	Passive	GC-MS	IPA	590		P
28	8.6	Epoxy resin	Printing	Impinger	Liquid trap	ISE	Fluorine^*	5.1		L
				Canister	Evacuated	GC-MS	Acetone	582
							IPA	1377
41	NR	MM resin	Printing	PID	10.6 eV	n/a	TVOC	1053		Q
			Curing and washing	PID	10.6 eV	n/a	TVOC	1774

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ABS = acrylonitrile butadiene styrene, CF = carbon fiber additive, FR = flame retardant additive, MM = methyl methacrylate, PC = polycarbonate, PET = polyethylene terephthalate, PETG = PET glycol, PLA = polylactic acid

3-DP = desktop-scale fused filament fabrication 3D printer, AVP = acetone vapor polishing task, CVP = chloroform (CHCl₃) vapor polishing task, FDM^™ = industrial-scale fused deposition modeling machine, MJF = multi-jet fusion machine

OE = optoelectronic nose, PID = photoionization detector, TD = thermal desorption

DNPH = 2,4-Dinitrophenylhydrazine-coated silica gel sorbent, EC = electrochemical sensor, eV = electron volt, NDIR = non-dispersive infrared, SC = semiconductor sensor, SVI = soil vapor intrusion

GC = gas chromatography, HPLC = high-performance liquid chromatography, ISE = ion selective electrode, LC = liquid chromatography, MS = mass spectrometry, UV = ultraviolet detector

2-BAME = 2-buteinic acid methyl ester, 2-Furn. = 2-furnapropanoic acid, 4-M-2-P = 4-methyl-2-pentanone, BEA = 2-(2-butoxyethoxy)ethyl acetate, BHT = butylated hydroxytoluene, CO = carbon monoxide, CO₂ = carbon dioxide, DCPS = decamethylcyclopentasiloxane, EM = ethyl methacrylate, I. Myristate = isopropyl myristate, IPA = isopropyl alcohol, Iso. acrylate = isobornyl acrylate, MC = methylene chloride, MM = methyl methacrylate, NDEE = N-[3,4-dimethylphenyl]-ethyl ester, PG = propylene glycol, TFP = tetrahydro-2-furnyl methyl pivalate, THF = tetrahydrofurfyl, TVOC = total volatile organic compounds, TVOC ΣVOC_i = TVOC calculated as sum of all individual VOCs on a sample

P = peak

A = Afshar-Mohajer et al. (2015), McDonnell et al. (2016), C = Steinle (2016), D = Mendes et al. (2017), E = Du Preez et al. (2018b), F = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Martin, et al. (2019b), G = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Menchaca, et al. (2019c), H = Väisänen et al. (2019), I = Bravi, Murmura, and Santos (2019), J = Youn et al. (2019), K = Chan et al. (2020), L = Zisook et al. (2020), M = Pinheiro et al. (2021), N = Damanhuri, Subki, et al. (2019b), O = Damanhuri, Hariri, et al. (2019a), P = Freiser et al. (2018), Q = Yang and Li (2018)

NR = not reported

total fluorine (aerosol and gas)

Table 5.

Summary of gas-phase exposures to additive manufacturing workers.

Room (m³)	ACH (hr⁻¹)	Feedstock^a	Scenario^b	Sampler^c	Specifics	Analysis^d	Substance^e	C (μg/m³)^f	Cit.^g
Material extrusion AM process category
40	NR	ABS, PLA Employee 1	3-DP	Badge	Passive	GC-MS	Acetone	300	A
40	NR	ABS, PLA Employee 1	3-DP/AVP	Badge	Passive	GC-MS	Acetone	6470
40	NR	ABS, PLA Employee 2	3-DP/AVP	Badge	Passive	GC-MS	Acetone	380
66	NR	ABS Employee 2	FDM^™	Badge	Passive	GC-MS	Acetone	7210
66	NR	PC Employee 2	FDM^™	Badge	Passive	GC-MS	Acetone	2610
66	NR	ABS, PC Employee 2	FDM^™	Badge	Passive	GC-MS	Acetone	290
Outdoors	N/A	PLA Employee 2	CVP	Badge	Passive	GC-MS	Acetone	4050
Outdoors	N/A	PLA Employee 2	CVP	Badge	Passive	GC-MS	Chloroform	180
66	NR	ABS, PC, Ultem^®	FDM^™	Badge	Passive	GC-MS	Acetone	40–1880	B
				Badge	Passive	GC-MS	Pentane	40–110
				Badge	Passive	GC-MS	Cyclohexane	10–40
				Badge	Passive	GC-MS	Ethanol	30–80
				Badge	Passive	GC-MS	Naphtha	2000–2300
66	NR	ABS, Ultem^®	FDM^™	Badge	Passive	GC-MS	Benzene	20–30
				Badge	Passive	GC-MS	Hexane	150–190
40	NR	ABS, PLA Employee 1	3-DP (n = 7)	Badge	Passive	GC-MS	Acetone	100	C

				Badge	Passive	GC-MS	Pentane	10
				Badge	Passive	GC-MS	Ethanol	10
				Badge	Passive	GC-MS	Naphthas	1450
40	NR	ABS/PLA Employee 2	3-DP (n = 7)	Badge	Passive	GC-MS	Acetone	50
				Badge	Passive	GC-MS	Pentane	30
				Badge	Passive	GC-MS	Hexane	220
				Badge	Passive	GC-MS	IPA	150
				Badge	Passive	GC-MS	Naphthas	2090
40	NR	ABS, PLA Employee 1	3-DP (n = 7)/AVP/Etoh	Badge	Passive	GC-MS	Acetone	2700
				Badge	Passive	GC-MS	Pentane	150
				Badge	Passive	GC-MS	Hexane	160
				Badge	Passive	GC-MS	Ethanol	100
				Badge	Passive	GC-MS	Naphthas	1330
40	NR	ABS Employee 2	3-DP	Badge	Passive	GC-MS	Acetone	1880
				Badge	Passive	GC-MS	Pentane	110
				Badge	Passive	GC-MS	Hexane	190
				Badge	Passive	GC-MS	Ethanol	30
				Badge	Passive	GC-MS	Naphthas	2140
76	NR	ABS	Printing	Badge	Passive	GC-MS	Acetone	40
				Badge	Passive	GC-MS	Pentane	40
				Badge	Passive	GC-MS	IPA	350
				Badge	Passive	GC-MS	Naphthas	2800
45	NR	PLA Day 1	3-DP	pPID	10.6 eV	n/a	TVOC	1.4 × 10⁴ (P)
45	NR	PLA Day 2	3-DP	pPID	10.6 eV	n/a	TVOC	1.8 × 10⁴ (P)
45	NR	PLA Day 3	3-DP	pPID	10.6 eV	n/a	TVOC	2.9 × 10⁴ (P)
45	NR	PLA	3-DP	Canister	Evacuated	GC-MS	Acetaldehyde	10–20
				Canister	Evacuated	GC-MS	Acetone	50–120
				Canister	Evacuated	GC-MS	Ethanol	40
				Canister	Evacuated	GC-MS	IPA	2700–9800
				Canister	Evacuated	GC-MS	MM	2
Material jetting AM process category
90	0.22 estimated	TangoBlack+, VeroClear	Printing	Badge	Passive	GC-MS	Acetone	20–80	B
				Badge	Passive	GC-MS	Pentane	10–60
				Badge	Passive	GC-MS	Ethanol	520–2020
				Badge	Passive	GC-MS	Naphtha	1530–1710
				Badge	Passive	GC-MS	IPA	70–520
Vat photopolymerization AM process category
NR	NR	White resin	Drilling models	Badge	Passive	GC-MS	IPA	590	D

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ABS = acrylonitrile butadiene styrene, PC = polycarbonate, PLA = polylactic acid

3-DP = desktop-scale fused filament fabrication 3D printer, AVP = acetone vapor polishing task, CVP = chloroform vapor polishing task, Etoh = cleaning build platform with ethanol, FDM^™ = industrial-scale fused deposition modeling machine

pPID = personal photoionization detector

GC-MS = gas chromatography-mass spectrometry

IPA = isopropyl alcohol, MC = methylene chloride, MM = methyl methacrylate, TVOC = total volatile organic compounds

P = peak

A = Du Preez et al. (2018b), B = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Martin, et al. (2019b), C = Stefaniak, Johnson, du Preez, Hammond, Wells, Ham, LeBouf, Menchaca, et al. (2019c), D = Freiser et al. (2018)

NR = not reported