DOT Hazard Class

Class 2.3

Toxic Gas

49 CFR §173.115(c)

Placard: White placard with skull-and-crossbones — INHALATION HAZARD

ERG entries

207

Divisions

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Packing groups

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Compat groups

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Definition

A gas that is known to be so toxic or corrosive to humans as to pose a hazard to health during transportation, OR in the absence of adequate human toxicity data has an LC50 value of not more than 5000 mL/m³.

Primary hazards

TIH (Toxic-by-Inhalation) — may be fatal if inhaled
Vapors may be heavier than air, spreading along the ground and collecting in low areas
May be corrosive to the eyes, skin, and mucous membranes
Contact with liquid may cause frostbite

Public safety response

Isolate initial spill or leak area 100 m (330 ft) minimum; for a large TIH release consult the Green pages (Table 1 Initial Isolation and Protective Action Distances). Evacuate downwind. Positive-pressure SCBA and fully encapsulating chemical protective clothing are required.

Common materials in this class

Anhydrous ammonia, chlorine, sulfur dioxide, hydrogen sulfide, phosgene, hydrogen cyanide, methyl bromide, chlorine dioxide.

UN1005Ammonia, anhydrous UN1017Chlorine UN1051Hydrogen cyanide, stabilized UN1076Phosgene UN1079Sulfur dioxide

Special provisions / notes

TIH Zone A/B/C/D classifies severity — Zone A (LC50 ≤ 200 ppm) is the most severe. Green Table 1 and Table 3 (large-spill) provide initial isolation distance and protective action distance for day/night.