Substance

pK_A [36]

Henry’s Constant [33]

IDLH [40]

LC_{(1, 0.5 h)} [41]

hydrogen sulfide

7 (pK_A1)

12 (pK_A2)

5.5

100 ppm

508 ppm

carbon dioxide

6.4

16.5

40,000 ppm

68,766 ppm

ammonia

9.2

0.03

300 ppm

3550 ppm

methane

not applicable

374

not available

not available