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Table 3 Severity of hazard criteria and scoring of chemicals

From: A screening tool to prioritize public health risk associated with accidental or deliberate release of chemicals into the atmosphere

Inhalational toxicity     Flammability     Reactivity
AEGL-3 or PAC-3 (mg/m3) for 60 min exposure Toxicity score NFPA flammability criteria* NFPA score NFPA reactivity criteria* NFPA score
≤1 4 Flammable gas or cryogenic material 4 Materials with instantaneous power density (IPD) of 1000 W/mL or greater @ 250°C; sensitive to localized thermal or mechanical shock at normal temperature and pressure 4
Liquid with flash point (FP) below 22.8°C and boiling point (BP) below 37°C
   Materials that spontaneously ignite when exposed to air    
>1, ≤10 3 Liquids with FP below 22.8°C and BP at or above 37.8°C; or FP at or above 22.8°C and below 37.8°C 3 Materials with IPD at or above 100 W/mL and below 1000 W/mL @ 250°C; sensitive to thermal or mechanical shock at elevated temperature and pressure 3
>10, ≤100 2 Liquids with FP at or above 37.8°C and below 93.4°C 2 Materials with IPD at or above 10 W/mL and below 100 W/mL @ 250°C 2
>100, ≤1000 1 Liquids, solids, semi-solids with FP above 93.4°C 1 Materials with IPD at or above 0.01 W/mL and below 10 W/mL @ 250°C 1
>1000 0 If assigned 0 by NFPA 0 Materials with IPD below 0.01 W/mL @ 250°C 0
  1. * See NFPA 704 for complete listing of criteria [30].