Table 2.

Indoor air styrene concentrations were compared against exposure levels for the general public and workers: (left) Public health and regulatory levels for exposure and the corresponding defined color indices, (right) The simulated peak styrene concentration and corresponding time to reach that concentration with the exhaust fan on and off.

COMPARISON LEVELS: Public Health and Regulatory Levels for Exposure and Color Indices
Color	Concentration (ppm)	Public Exposure Level	Worker Exposure Level
	< 0.0028	-	-
	0.0028 – 0.23	Odor Threshold (AIHA, 2013) (min 0.0028 ppm)
	0.23 – 4.9	USEPA Rfc (ATSDR, 1992) (0.23 ppm)	-
	4.9 – 8	Cal EPA OEHHA AREL (OEHHA, 1999) (4.9 ppm)	-
	8 – 20	USEPA NOAEL (USEPA, 1999) (8 ppm)	-
	20 – 40	USEPA, AEGL-1 (USEPA, 2020a) (20 ppm)	ACGIH TWA (ACGIH, 1999) (20 ppm)
	40 – 50	-	ACGIH STEL (ACGIH, 1999) (40 ppm)
	50 – 100	-	NIOSH TWA (NIOSH, 2020); AIHA ERPG-1 (AIHA, 1998) (50 ppm)
	100 – 200	-	OSHA TWA (OSHA, 2020); NIOSH STEL (NIOSH, 2020) (100 ppm)
	200 −250	-	OSHA C (OSHA, 2020) (200 ppm)
	250 – 700	-	AIHA ERPG-2 (AIHA, 1998) (250 ppm); USEPA AEGL-2 (USEPA, 2020a) (230 ppm)
	> 700	-	NIOSH IDLH (NIOSH, 2020) (700 ppm)

RESULTS: Peak Concentration and Corresponding Time to Reach that Level
Scenario	Observed Concentration (corresponding time) [unit: ppm (min)]
	Exhaust Fan On				Exhaust Fan Off
	Floor gap: 81.28 cm × 0 cm	81.28 cm × 2.54 cm	81.28 cm × 0 cm	81.28 cm × 2 m
SIM 1	0.03 (0.79)	0.02 (0.65)	0.01 (0.64)	0.0007 (0.70)	0.002 (1.33)
SIM 2	8.90 (0.66)	5.88 (0.67)	4.45 (0.74)	0.22 (0.68)	0.50 (1.31)
SIM 3	29.68 (0.66)	19.56 (0.78)	14.84 (0.70)	0.74 (0.63)	1.65 (1.37)
SIM 4	0.03 (1.26)	0.02 (0.65)	0.01 (1.34)	0.0008 (1.46)	0.002 (1.75)
SIM 5	8.90 (0.66)	6.08 (1.25)	4.70 (1.26)	0.23 (1.25)	0.51 (1.80)
SIM 6	30.97 (1.24)	20.07 (1.28)	14.84 (0.70)	0.76 (1.30)	1.78 (1.58)
SIM 7	0.80 (9.72)	0.53 (9.84)	0.40 (9.71)	0.02 (9.66)	0.08 (10.04)
SIM 8				6.08 (10.07)	23.71 (10.13)
SIM 9				19.98 (9.72)	77.23 (10.08)
SIM 10	0.80 (9.75)	0.54 (10.18)	0.40 (9.80)	0.02 (9.66)	0.08 (10.11)
SIM 11				6.03 (9.82)	21.90 (10.34)
SIM 12				20.01 (9.75)	77.08 (10.00)

Abbreviations: ACGIH=American Conference of Governmental Industrial Hygienists, AEGL=Acute Exposure Guideline Level, AIHA=American Industrial Hygiene Association, AREL=Acute Reference Exposure Level, C=Ceiling, USEPA=US Environmental Protection Agency, ERPG=Emergency Response Planning Guidelines, IDLH=Immediately dangerous to life or health, NIOSH=National Institute for Occupational Safety and Health, NOAEL=No observed effect level, OEHHA=Office of Environmental Health Hazard Assessment, OSHA=Occupational Safety and Health Administration, Rfc=Reference concentration, STEL=Short Term Exposure Limit, and TWA=Time-weighted Average