Table 1.

Carpets as an exposure source.

Authors [Reference]	Type of Study	Results
Dybendal et al. [6]	Comparison of dust, proteins and allergens from carpeted and smooth floors in homes and schools in Norway.	Carpeted floors in schools and homes contained significantly more dust, proteins, and allergens than smooth floors.
Van Strien et al. [7]	Measurements of mite allergen concentrations in floor- and mattress dust in dwellings.	Mite allergen concentrations in dust from carpeted floors were 6–14 times higher than in dust from smooth floors.
Zock et al. [8]	Comparison of house dust mite allergen levels in dust from schools with smooth and carpeted classroom floors.	More house dust mite allergen in dust from carpeted classroom floors than from smooth classroom floors, but the levels were much lower than in dust from floors in homes.
Tranter [9]	Review article.	Higher concentrations of allergens consistently found in carpets compared with smooth floors. Carpet vacuuming seems to remove larger particles but not the allergen-associated smaller particles whereas smooth floor cleaning appears more efficient regarding removal of these smaller particles.
Causer et al. [10]	Effect of carpet construction on content and vertical distribution of mite allergen.	Significantly higher concentrations of allergens from house dust mites have been reported in rooms with carpet floors no matter how the carpets were made compared to hard/smooth floors.
Arbes et al. [11]	Levels of seven indoor allergens in 89 day-care facilities in two North Carolina counties. Dust samples were collected from carpeted and non-carpeted areas of one room each place.	Levels of several antigens were statistically higher on carpet than on hard surfaced flooring. For dog and cat allergens, the differences were clinically significant, with mean levels on hard floors being well below proposed thresholds for allergic sensitization.
Cho et al. [12]	The effect of home characteristics on dust antigen concentrations in homes.	Carpeted floor held larger amount of antigens than non-carpeted floor.
Matheson et al. [13]	Residential characteristics predict changes in Der p 1, Fel d 1 and ergosterol but not fungi over time.	Installation of carpets caused an increased exposure to allergens from house dust mites. Removal of carpets significantly reduced the levels of both mite allergens and ergosterol, a cell wall component of molds.
Dahl et al. [5]	Textile floor coverings as part of indoor environment.	Significantly larger amount of dust and viable microorganisms in carpet floors compared to hard floors did not result in observed differences in dust fall rates on inventory surfaces or particle content in room air.
Salo et al. [14]	Investigation of indoor allergens in school and day care environments.	Carpeted floors, upholstered furniture and clothes were important reservoirs and sources of allergens, especially from dust mites and pets.
Ashley et al. [15]	Evaluation of a standardized micro-vacuum sampling method for collection of surface dust.	When comparing the recovery fraction obtained by vacuuming of standardized dust applied to various surfaces, significantly lower amounts were obtained from rough and porous surfaces compared with smooth and hard surfaces and with the lowest recovery from carpets.
Stranger et al. [16]	Comparative study of indoor air quality in Belgian schools.	The ratio between indoor air and outdoor air amounts of particulate matter (<2.5 mm) was significantly higher for classrooms with carpeted floors compared with classroom without carpet floor. This indicated that carpets may increase the amount of resuspended dust.
Tian et al. [17]	A comparative study of walking-induced dust resuspension using a consistent test mechanism.	For particle size 3.0–10.0 µm, carpets exhibited higher resuspension fractions compared with hard floorings. The results support that people sensitive to allergens could select hard floorings to reduce exposure and adverse health outcomes.
Bramwell et al. [18]	An evaluation of the impact of flooring types on exposures to fine and coarse particles.	Flooring type can significantly impact incremental time-averaged daily exposures to coarse and fine particles and that high-density cut pile carpeting resulted in the highest exposures.
Paton et al. [19]	Study of re-aerosolization of spores from flooring surfaces.	Walking on a carpet generated significantly more re-aerosolization of spores than walking on PVC. Heavy contra light walking as well as height above the flooring material where sampling was done all had an impact on the amount of re-aerosolization levels.
Siming et al. [20]	Chamber study.	Higher resuspension rates of particles from carpets compared to wood PVC and vinyl materials.
Salimifard et al. [21]	Chamber study.	Carpet surfaces yields higher resuspension rate than linoleum surface at the same humidity level.
Scheepers et al. [22]	The effect on indoor air quality of new carpet combined with air filtration investigated in classrooms.	The combination resulted in reduced levels of particles and VOC in air compared with hard floors alone. No assessment was done on carpets alone.