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The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment." Examples include smoke or other poisonous gases at sufficiently high concentrations. It is calculated using the LD50 or LC50.[1] The Occupational Safety and Health Administration (OSHA) regulation (1910.134(b)) defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere."[2]
IDLH values are often used to guide the selection of breathing apparatus that are made available to workers or firefighters in specific situations.[1]
The NIOSH definition does not include oxygen deficiency (below 19.5%) although atmosphere-supplying breathing apparatus is also required.[3] Examples include high altitudes and unventilated, confined spaces.
The OSHA definition is arguably broad enough to include oxygen-deficient circumstances in the absence of "airborne contaminants", as well as many other chemical, thermal, or pneumatic hazards to life or health (e.g., pure helium, super-cooled or super-heated air, hyperbaric or hypo-baric or submerged chambers, etc.). It also uses the broader term "impair", rather than "prevent", with respect to the ability to escape. For example, blinding but non-toxic smoke could be considered IDLH under the OSHA definition if it would impair the ability to escape a "dangerous" but not life-threatening atmosphere (such as tear gas).
The OSHA definition is part of a legal standard, which is the minimum legal requirement. Users or employers are encouraged to apply proper judgment to avoid taking unnecessary risks, even if the only immediate hazard is "reversible", such as temporary pain, disorientation, nausea, or non-toxic contamination.
NIOSH respirator selection logic
If the concentration of harmful substances is IDLH, the worker must use the most reliable respirators. Such respirators should not use cartridges or canister with the sorbent, as their lifetime is too poorly predicted. In addition, the respirator must maintain positive pressure under the mask during inspiration, as this will prevent the leakage of unfiltered air through the gaps (which occur between the edges of the mask and the face sometimes).
Textbook NIOSH[4] recommended for use in IDLH conditions only pressure-demand self-contained breathing apparatus with a full facepiece, or pressure-demand supplied-air respirator equipped with a full facepiece in combination with an auxiliary pressure-demand self-contained breathing apparatus.
IDLH values
The following examples are listed in reference to IDLH values.[3]
Legend:[5]
- Ca
- NIOSH considers this substance to be a potential occupational carcinogen. Revised values may follow in parentheses.
- N.D.
- Not determined. That is, the level is unknown, not non-existent.
- 10%LEL
- The IDLH value has been set at 10% of the lower explosive limit although other irreversible health effects or impairment of escape due to toxicology exist only at higher levels.
IDLH values for gases and vapors, used in industry | ||||||
---|---|---|---|---|---|---|
Number | Substance | IDLH value | Source | |||
CAS | ICSC | mg/m3 | ppm | |||
75-07-0 | 0009 | Acetaldehyde | 3600 mg/m3 | 2000 ppm | 75070 Archived 2015-10-02 at the Wayback Machine | |
64-19-7 | 0363 | Acetic acid | 123 mg/m3 | 50 ppm | 64197 | |
108-24-7 | 0209 | Acetic anhydride | 836 mg/m3 | 200 ppm | 108247 | |
67-64-1 | 0087 | Acetone | 5900 mg/m3 | 2500 ppm | 67641 (10% Lower explosive limit LEL) | |
75-05-8 | 0088 | Acetonitrile | 840 mg/m3 | 500 ppm | 75058 Archived 2015-10-02 at the Wayback Machine | |
79-27-6 | 1235 | Acetylene tetrabromide | 113.1 mg/m3 | 8 ppm | 79276 | |
107-02-8 | 0090 | Acrolein | 4.58 mg/m3 | 2 ppm | 107028 | |
79-06-1 | 0091 | Acrylamide | 60 mg/m3 | - | 79061, carcinogenic substance | |
107-13-1 | 0092 | Acrylonitrile | 184.45 mg/m3 | 85 ppm | 107131 | |
309-00-2 | 0774 | Aldrin | 25 mg/m3 | - | 309002, carcinogenic substance | |
107-18-6 | 0095 | Allyl alcohol | 47.6 mg/m3 | 20 ppm | 107186 | |
107-05-1 | 0010 | Allyl chloride | 782.5 mg/m3 | 250 ppm | 107051 | |
106-92-3 | 0096 | Allyl glycidyl ether | 233.5 mg/m3 | 50 ppm | 106923 | |
504-29-0 | 0214 | 2-Aminopyridine | 19.25 mg/m3 | 5 ppm | 504290 | |
7664-41-7 | 0414 | Ammonia | 210 mg/m3 | 300 ppm | 7664417 | |
7773-06-0 | 1555 | Ammonium sulfamate | 1500 mg/m3 | - | 7773060 | |
628-63-7 | 0218 | n-Amyl acetate | 5330 mg/m3 | 1000 ppm | 628637 | |
626-38-0 | 0219 | sec-Amyl acetate | 5330 mg/m3 | 1000 ppm | 626380 | |
62-53-3 | 0011 | Aniline | 381 mg/m3 | 100 ppm | 62533, carcinogenic substance | |
90-04-0 | 0970 | o-Anisidine | 50 mg/m3 | - | 90040 | |
104-94-9 | 0971 | p-Anisidine | 50 mg/m3 | - | 104949 | |
7440-36-0 | 0775 | Antimony | 50 mg/m3 | - | 7440360 | |
86-88-4 | 0973 | ANTU | 100 mg/m3 | - | 86884 | |
7440-38-2 | 0013 | Arsenic | 5 mg/m3 | - | 7440382 | |
7784-42-1 | 0222 | Arsine | 9.57 mg/m3 | 3 ppm | 7784421, carcinogenic substance | |
86-50-0 | 0826 | Azinphos-methyl | 10 mg/m3 | - | 86500 | |
10361-37-2 | 0614 | Barium chloride | 50 mg/m3 | - | 7440393 Archived 2015-10-02 at the Wayback Machine | |
10022-31-8 | 1480 | Barium nitrate | 50 mg/m3 | - | 7440393 Archived 2015-10-02 at the Wayback Machine | |
71-43-2 | 0015 | Benzene | 1595 mg/m3 | 500 ppm | 71432, carcinogenic substance | |
94-36-0 | 0225 | Benzoyl peroxide | 1500 mg/m3 | - | 94360 | |
100-44-7 | 0016 | Benzyl chloride | 51.8 mg/m3 | 10 ppm | 100447 | |
7440-41-7 | 0226 | Beryllium & beryllium compounds | 4 mg/m3 | - | 7440417 | |
1303-86-2 | 0836 | Boron oxide | 2000 mg/m3 | - | 1303862 | |
7637-07-2 | 0231 | Boron trifluoride | 69.3 mg/m3 | 25 ppm | 7637072 | |
7726-95-6 | 0107 | Bromine | 19.6 mg/m3 | 3 ppm | 7726956 | |
75-25-2 | 0108 | Bromoform | 8789 mg/m3 | 850 ppm | 75252 | |
106-99-0 | 0017 | 1,3-Butadiene | 4420 mg/m3 | 2000 ppm | 106990, (10% Lower explosive limit LEL); carcinogenic substance | |
78-93-3 | 0179 | 2-Butanone | 8850 mg/m3 | 3000 ppm | 78933 | |
111-76-2 | 0059 | 2-Butoxyethanol | 3381 mg/m3 | 700 ppm | 111762 | |
123-86-4 | 0399 | n-Butyl acetate | 8075 mg/m3 | 1700 ppm | 123864, (10% Lower explosive limit LEL) | |
105-46-4 | 0840 | sec-Butyl acetate | 8075 mg/m3 | 1700 ppm | 105464 (10% Lower explosive limit LEL) | |
540-88-5 | 1445 | tert-Butyl acetate | 7125 mg/m3 | 1500 ppm | 540885, (10% Lower explosive limit LEL) | |
71-36-3 | 0111 | n-Butyl alcohol | 4242 mg/m3 | 1400 ppm | 71363 | |
78-92-2 | 0112 | sec-Butyl alcohol | 6060 mg/m3 | 2000 ppm | 78922 | |
75-65-0 | 0114 | tert-Butyl alcohol | 4848 mg/m3 | 1600 ppm | 75650 | |
109-73-9 | 0374 | n-Butylamine | 897 mg/m3 | 300 ppm | 109739 | |
1189-85-1 | 1533 | tert-Butyl chromate | 15 mg/m3 | - | 1189851, carcinogenic substance | |
2426-08-6 | 0115 | n-Butyl glycidyl ether | 1332.5 mg/m3 | 250 ppm | 2426086 | |
109-79-5 | 0018 | n-Butyl mercaptan | 1845 mg/m3 | 500 ppm | 109795 | |
98-51-1 | 1068 | p-tert-Butyltoluene | 607 mg/m3 | 100 ppm | 98511 | |
7440-43-9 | 0020 | Cadmium dust | 9 mg/m3 | - | 7440439, carcinogenic substance | |
1306-19-0 | 0020 | Cadmium fume | 9 mg/m3 | - | 7440439, carcinogenic substance | |
7778-44-1 | 0765 | Calcium arsenate | 5 mg/m3 | - | 7778441, carcinogenic substance | |
1305-78-8 | 0409 | Calcium oxide | 25 mg/m3 | - | 1305788 | |
76-22-2 | 1021 | Camphor | 200 mg/m3 | - | 76222 | |
63-25-2 | 0121 | Carbaryl | 100 mg/m3 | - | 63252 | |
1333-86-4 | 0471 | Carbon black | 1750 mg/m3 | - | 1333864 | |
124-38-9 | 0021 | Carbon dioxide | 72000 mg/m3 | 40000 ppm | 124389 | |
75-15-0 | 0022 | Carbon disulfide | 1555 mg/m3 | 500 ppm | 75150 | |
630-08-0 | 0023 | Carbon monoxide | 1380 mg/m3 | 1200 ppm | 630080 | |
56-23-5 | 0024 | Carbon tetrachloride | 1258 mg/m3 | 200 ppm | 56235, carcinogenic substance | |
57-74-9 | 0740 | Chlordane | 100 mg/m3 | - | 57749, carcinogenic substance | |
8001-35-2 | 0843 | Chlorinated camphene | 200 mg/m3 | - | 8001352, carcinogenic substance | |
31242–93–0 | - | Chlorinated diphenyl oxide | 5 mg/m3 | - | 31242930 | |
7782-50-5 | 0126 | Chlorine | 29 mg/m3 | 10 ppm | 7782505 | |
10049-04-4 | 0127 | Chlorine dioxide | 13.35 mg/m3 | 5 ppm | 10049044 | |
7790-91-2 | 0656 | Chlorine trifluoride | 75.6 mg/m3 | 20 ppm | 7790912 | |
107-20-0 | 0706 | Chloroacetaldehyde | 144.5 mg/m3 | 45 ppm | 107200 | |
532-27-4 | 0128 | α-Chloroacetophenone | 15 mg/m3 | - | 532274 | |
108-90-7 | 0642 | Chlorobenzene | 4610 mg/m3 | 1000 ppm | 108907 | |
2698-41-1 | 1065 | o-Chlorobenzylidene malonitrile | 2 mg/m3 | - | 2698411 | |
74-97-5 | 0392 | Chlorobromomethane | 10580 mg/m3 | 2000 ppm | 74975 | |
53469-21-9 | 0175 | Chlorodiphenyl (42% chlorine) | 5 mg/m3 | - | 53469219, carcinogenic substance | |
11097-69-1 | 0939 | Chlorodiphenyl (54% chlorine) | 5 mg/m3 | - | 53469219, carcinogenic substance | |
67-66-3 | 0027 | Chloroform | 2440 mg/m3 | 500 ppm | 67663, carcinogenic substance | |
600-25-9 | 1423 | 1-Chloro-1-nitropropane | 5.06 mg/m3 | 100 ppm | 600259 | |
76-06-2 | 0750 | Chloropicrin | 13.44 mg/m3 | 2 ppm | 76062 | |
126-99-8 | 0133 | β-Chloroprene | 10.86 mg/m3 | 300 ppm | 126998, carcinogenic substance | |
1333-82-0 | 1194 | Chromium trioxide | 15 mg/m3 | - | 1333820, carcinogenic substance | |
- | - | Chromium(II) | 250 mg/m3 | - | cr2m3 | |
- | - | Chromium(III) | 25 mg/m3 | - | cr3m3 | |
7440-47-3 | 0029 | Chromium | 250 mg/m3 | - | 7440473 | |
65996-93-2 | 1415 | Coal tar pitch volatiles | 80 mg/m3 | - | 65996932, carcinogenic substance | |
7440-48-4 | 0782 | Cobalt | 20 mg/m3 | - | 7440484 | |
7440-50-8 | 0240 | Copper | 100 mg/m3 | - | 7440508 | |
- | - | Cotton dust (raw) | 100 mg/m3 | - | cotdust | |
136-78-7 | 1142 | Crag® herbicide | 500 mg/m3 | - | 136787 | |
108-39-4 | 0646 | m-Cresol | 1107.5 mg/m3 | 250 ppm | cresol | |
95-48-7 | 0030 | o-Cresol | 1107.5 mg/m3 | 250 ppm | cresol | |
106-44-5 | 0031 | p-Cresol | 1107.5 mg/m3 | 250 ppm | cresol | |
4170-30-3 | 0241 | Crotonaldehyde | 143.5 mg/m3 | 50 ppm | 123739 | |
98-82-8 | 0170 | Cumene | 4428 mg/m3 | 900 ppm | 98828 (10% Lower explosive limit LEL) | |
110-82-7 | 0242 | Cyclohexane | 4472 mg/m3 | 1300 ppm | 110827 | |
108-93-0 | 0243 | Cyclohexanol | 1640 mg/m3 | 400 ppm | 108930 | |
108-94-1 | 0425 | Cyclohexanone | 2814 mg/m3 | 700 ppm | 108941 | |
110-83-8 | 1054 | Cyclohexene | 6720 mg/m3 | 2000 ppm | 110838 | |
542-92-7 | 0857 | Cyclopentadiene | 2025 mg/m3 | 750 ppm | 542927 (10% Lower explosive limit LEL) | |
13121-70-5 | - | Cyhexatin | 80 mg/m3 (25 mg/m3 - for Sn) | - | tin-org | |
94-75-7 | 0033 | 2,4-D | 100 mg/m3 | - | 94757 | |
50-29-3 | 0034 | DDT | 500 mg/m3 | - | 50293, carcinogenic substance | |
17702-41-9 | 0712 | Decaborane | 15 mg/m3 | - | 17702419 | |