The following explanations of the four hazards are based upon protective equipment normally used by firefighters.
4. Materials too dangerous to health to expose firefighters. A few whiffs of the vapor could death, or the vapor or liquid could be fatal upon penetrating the firefighter’s normal full-protective clothing. The normal full-protective clothing and breathing apparatus available to the average fire department will not provide adequate protection against inhalation or skin contact with these materials.
3. Materials extremely hazardous to health, but areas may be entered with extreme care. Full-protective clothing self-contained breathing apparatus, coat, pants, gloves, boot, and bands around legs, arms, and waist should be provided. No skin surface should be exposed.
2. Materials hazardous to health, but areas may be entered freely with full-faced mask and self-contained breathing apparatus that provides eye protection.
1. Materials only slightly hazardous to health. It may be desirable to wear self-contained breathing apparatus.
0. Materials that on exposure under fire condition would offer no hazard beyond that of ordinary combustible material.