Flammability (Red) 4 - Materials which will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature or which are readily dispersed in air, and which will burn readily. This degree should include: Gases; Cryogenic materials; Any liquid or gaseous material which is a liquid while under pressure and have a flash point below 73F (22.8C) and having a boiling point below 100F(37.8C). (Class IA flammable liquids.) Materials which on account of their physical form or environmental conditions can form explosive mixtures with air and which are readily dispersed in air, such as dusts of combustible solids and mists of flammable or combustible liquid droplets. 3 - Liquids and solids that can be ignited under almost all ambient temperature conditions. Materials in this degree produce hazardous atmospheres with air under almost all ambient temperatures or, though unaffected by ambient temperatures, are readily ignited under almost all conditions. This degree should include: Liquids having a flash point below 73F (22.8C) and having a boiling point at or above 100F (37.8C) and those liquids having a flash point at or above 73F (22.8C) and below 100F (37.8C). (Class IB and Class IC flammable liquids); Solid materials in the form of coarse dusts which may burn rapidly but which are generally do not form explosive atmospheres with air; Solid materials in a fibrous or shredded form which may burn rapidly and create flash fire hazards, such as cotton, sisal and hemp; Materials which burn with extreme rapidity, usually by reason of self-contained oxygen (e.g., dry nitrocellulose and many organic peroxides); Materials which ignite spontaneously when exposed to air. 2 - Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur. Materials in this degree would not under normal conditions form hazardous atmospheres with air, but under high ambient temperatures or under moderate heating may release vapor in sufficient quantities to produce hazardous atmospheres with air. This degree should include: Liquids having a flash point above 100F (37.8C), but not exceeding 200F (93.4F); Solids and semisolids which readily give off flammable vapors. 1 - Materials that must be preheated before ignition can occur. Materials in this degree require considerable preheating, under all ambient temperature condition, before ignition and combustion can occur. This degree should include: Materials which will burn in air when exposed to a temperature of 1500F (815.5C) for a period of 5 minutes or less; Liquids, solids, and semisolids having a flash point above 200F (93.4C); This degree includes most ordinary combustible materials. 0 - Materials that will not burn. This degree should include any material which will not burn in air when exposed to a temperature of 1500F (815.5C) for a period of 5 minutes. Health (Blue) 4 - 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. 3 - 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. 2 - 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. 1 - Materials which on exposure would cause irritation but only minor residucal 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. 0 - Materials which on exposure under fire conditons would offer no hazard beyond that of ordinary combustible material. Reactivity (Yellow) 4 - Materials which in themselves are readily capable of detonation or of explosive decomposition or explosive reaction at normal temperatures and pressures. This degree should include materials which are sensitive to mechanical or localized thermal shock at normal temperatures and pressures. 3 - Materials which in themselves are capable of detonation or of explosive reaction but which require a strong initiating source or which must be heated under confinement before initiation. This degree should include materials which are sensitive to thermal or mechanical shock at elevated temperatures and pressures or which react explosively with water without requiring heat or confinement. 2 - Materials which in themselves are normally unstable and readily undergo violent chemical change but do not detonate. This degree should include materials which can undergo chemical change with rapid release of energy at normal temperatures and pressures or which can undergo violent chemical change at elevated temperatures and pressures. It should also include those materials which may react violently with water or which may form potentially explosive mixtures with water. 1 - Materials which in themselves are normally stable, but which can become unstable at elevated temperatures and pressures or which may react with wtaer with some release of energy but not violently. 0 - Materials which in themselves are normally stable, even under fire exposure conditions, and which are not reactive with water. Special Notice (White) The fourth, white, field of the hazard signal can have variable content, depending on who prepared the signal. The 1990 edition of the National Fire Codes (section 704, chapter 5) specifies only two symbols. Additional symbols are commonly included. The field may also be left blank if no special hazards are present. BACK