Materials which upon very limited exposure could cause death or major residual injury even though prompt medical treatment is given, including those which are too dangerous to be approached without specialized protective equipment. This degree should include:

• Materials which can penetrate ordinary rubber protective clothing;
• Materials which under normal conditions or under fire conditions give off gases which are extremely hazardous (i.e., toxic or corrosive) through inhalation or through contact with or absorption through the skin.

Materials which upon short-term exposure could cause serious temporary or residual injury even though prompt medical treatment is given, including those requiring protection from all bodily contact. This degree should include:

• Materials giving off highly toxic combustion products;
• Materials corrosive to living tissue or toxic by skin absorption.

Materials which on intense or continued exposure could cause temporary incapacitation or possible residual injury unless prompt medical treatment is given, including those requiring use of respiratory protective equipment with independent air supply. This degree should include:

• Materials giving off toxic combustion products;
• Materials giving off highly irritating combustion products;
• Materials which either under normal conditions or under fire conditions give off toxic vapors lacking warning properties.

Materials which on exposure would cause irritation but only minor residual injury even if no treatment is given, including those which require use of an approved canister type gas mask. This degree should include:

• Materials which under fire conditions would give off irritating combustion products
• Materials which on the skin could cause irritation without destruction of tissue.

Materials which on exposure under fire conditions would offer no hazard beyond that of ordinary combustible material.