Table 3.

Airborne hydrogen sulfide exposure limits established by various U.S. and international public safety organizations.

Agency	Exposure Level Types	REL (ppm)	Reference
ACGIH	TLV-TWA	1	OSHA [63]
	TLV-STEL	5
AIHA	ERPG 1a	0.1	AIHA [64]
	ERPG 2	30
	ERPG 3	100
ATSDR	MRL-Acute	0.07	ATSDR [23]
	MRL-Intermediate	0.02
	MRL-Chronic	n/a
DOE	PAC-1	0.51	DOE [65]
	PAC-2	27
	PAC-3	50
EPA	RfC	0.001	EPA [51]
	AEGL-1: 10 min	0.75	NRC [66]
	30 min	0.60
	60 min	0.51
	4 hr	0.36
	8 hr	0.33
	AEGL-2: 10 min	41
	30 min	32
	60 min	27
	4 hr	20
	8 hr	17
	AEGL-3: 10 min	76
	30 min	59
	60 min	50
	4 hr	37
	8 hr	31
DFG	MAK	5	DFG [67]
IARC	Carcinogenicity classification	n/a	IARC [68]
NIOSH	IDLH	100	NIOSH [69]
	REL: 10-min	10
OSHA	PEL (8-hour TWA) – general industry	n/a	OSHA [63]
	PEL Ceiling	20
	PEL Peak: 10 min	50
WHO	TWA: 24 hr	0.10	WHO [70] b
Range: 1 ppb – 100 ppm

^aERPGs estimate the concentrations at which most people will begin to experience health effects if they are exposed to a hazardous airborne chemical for 1 hour. (Sensitive members of the public are not covered by these guidelines; they may experience adverse effects at concentrations below the ERPG values.) A chemical may have up to three ERPG values, each of which corresponds to a specific tier of health effects:

ERPG-3 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.

ERPG-2 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual’s ability to take protective action.

ERPG-1 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient health effects or perceiving a clearly defined, objectionable odor.

^bWhile not discussed in WHO’s 2010 report on select air pollutants, the World Health Organization did publish air quality guidelines on H₂S in this report from 2000.

Abbreviations & Definitions (alphabetical): ACGIH = American Conference of Governmental Industrial Hygienists; AEGL = acute exposure guideline level; AEGL-1 = nondisabling threshold limit; AEGL-2: disabling threshold limit; AEGL-3: lethality threshold limit; AIHA = American Industrial Hygiene Association; ATSDR = Agency for Toxic Substances and Disease Registry; DFG = Deutsche Forschungsgemeinschaft; DOE = U.S. Department of Energy; ERPG = emergency response planning guideline; IDLH = immediately dangerous to life and health; IARC = International Agency for Research on Cancer; MAK = maximum workplace concentration across an 8-hour day, 40- hour work week; MRL = minimum risk level (inhalation factors, not oral, have been derived); MRL-Acute = MRL for acute-duration inhalation exposure (≤14 days); MRL-Chronic = MRL for chronic-duration inhalation; MRLIntermediate = MRL for intermediate-duration inhalation exposure (15–364 days); NAS = National Academy of Sciences; NIOSH = National Institute for Occupational Safety and Health; NRC = National Research Council; OSHA = Occupational Safety and Health Administration; PAC-1 = All protective action criteria correspond to 60-minute AEGL values. PAC-1 is for mild, transient health effects; PAC-2 = irreversible or other serious health effects that could impair the ability to take protective action; PAC-3 = life-threatening health effects; PEL = permissible exposure limit; PEL Peak: 10 min = acceptable maximum peak above ceiling over an 8-hour shift for 10 minutes once only if no other measured exposure occurs; PPM = parts per million; REL = recommended exposure limit; RfC = daily inhalation exposure limit over a lifetime that does not present risk of deleterious effects; TLV-STEL = threshold limit value – short-term exposure limit; TLV-TWA = threshold limit value – time weighted average.