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Nitric oxide

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 10102–43–9

NIOSH REL: 25 ppm (30 mg/m3) TWA

Current OSHA PEL: 25 ppm (30 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 25 ppm (31 mg/m3) TWA

Description of substance: Colorless gas.

LEL: . . . Nonflammable Gas

Original (SCP) IDLH: 100 ppm

Basis for original (SCP) IDLH: No useful data on acute inhalation toxicity are available on which to base the IDLH for nitric oxide. The chosen IDLH, therefore, is based on the statement by Sax [1975] that 100 to 150 ppm oxides of nitrogen are dangerous for short exposures of 30 to 60 minutes. The chosen IDLH seems reasonable because NIOSH [1976] cited a rabbit 15-minute LC50 of 315 ppm for nitric oxide [Carson et al. 1962].

Short-term exposure guidelines: None developed


Lethal concentration data:

SpeciesReferenceLC50 (ppm)LCLo (ppm)TimeAdjusted 0.5-hr


Derived value




Carson et al. 1962

Flury and Zernik 1931

Ivanov and Szubaev 1979

Pflesser 1935









15 min

12 min

4 hr


249 ppm (0.79)

1,850 ppm (0.74)

1,709 ppm (2.0)


25 ppm

185 ppm

171 ppm


Other animal data: Guinea pigs have survived an exposure at 175 ppm for an unstated period [Bodansky 1951].

Human data: It has been stated that exposures to oxides of nitrogen between 100 and 150 ppm are dangerous for exposures of 30 to 60 minutes [Sax 1975].

Revised IDLH: 100 ppm [Unchanged]

Basis for revised IDLH: Based on acute inhalation toxicity data in humans [Sax 1975], the original IDLH for nitric oxide (100 ppm) is not being revised at this time.


1. Bodansky O [1951]. Methemoglobinemia and methemoglobin-producing compounds. Pharmacol Rev 3:144-195.

2. Carson TR, Rosenholtz MS, Wilinski FT, Weeks MH [1962]. The responses of animals inhaling nitrogen dioxide for single, short-term exposures. Am Ind Hyg Assoc J 23:457-462.

3. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, pp. 157-165 (in German).

4. Ivanov NG, Szubaev EN [1979]. About the limitation of the content of nitrogen dioxide in the air of the working zone. Toksikol Nov Prom Khim Vesh 15:53-58 (in Russian).

5. NIOSH [1976]. QX05250. Nitrogen monoxide. In: Registry of toxic effects of chemical substances, 1976 ed. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-191, p. 780.

6. Pflesser G [1935]. The significance of nitric oxide in poisoning by nitrous gases. Arch Exp Pathol Pharmakol 179:545-557 (in German).

7. Sax NI [1975]. Nitric oxide. In: Dangerous properties of industrial materials. 4th ed. New York, NY: Van Nostrand Reinhold Company, pp. 961-962.

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