Hazardous Materials Awareness for Firefighters Flashcards

A tanker truck is involved in a highway accident. You observe a diamond-shaped placard with the number '1993' and the word 'FLAMMABLE.' What does the four-digit number on the placard represent?

Answer: The UN/NA identification number used to look up the specific hazardous material in reference guides

The four-digit number on a DOT placard is the UN (United Nations) or NA (North American) identification number. First responders use this number to look up the specific material in the Emergency Response Guidebook (ERG) to identify hazards and initial response actions. UN 1993 is flammable liquids (such as diesel fuel).

A chemical storage facility has an NFPA 704 placard posted on the door. The placard shows: Blue = 3, Red = 2, Yellow = 1, White = W (no water). What does the blue section (Health = 3) indicate?

Answer: The material can cause serious or permanent injury with short-term exposure

On the NFPA 704 diamond, the blue section indicates HEALTH hazard on a scale of 0–4. A rating of 3 means short-term exposure could cause serious or permanent injury. Blue = Health, Red = Flammability, Yellow = Instability/Reactivity, White = Special hazards. A rating of 4 is the highest and means the material can be lethal.

A hazardous materials incident involves an unknown liquid leaking from a derailed tank car. Which of the following should be the first action taken by arriving firefighters?

Answer: Approach from upwind and uphill, establish a safe perimeter, and identify the material from a distance using placards or the Emergency Response Guidebook

At an unknown hazmat incident, the first priority is life safety — including the safety of responders. Approach from upwind and uphill to avoid exposure, establish a safe perimeter to protect the public, and identify the material before committing personnel. Applying water to an unknown substance could be catastrophic (e.g., water-reactive materials).

A chemical has a vapor density of 1.8. What does this property mean for firefighter operations at an incident involving this material?

Answer: The vapor is heavier than air and will sink, accumulating in low areas such as basements, drains, and pits

Vapor density is compared to air, which has a vapor density of 1.0. A vapor density greater than 1.0 means the gas is heavier than air and will accumulate in low-lying areas — creating ignition or asphyxiation hazards in basements, drainage systems, and trenches. Methane (vapor density 1.0) sinks.

The Emergency Response Guidebook (ERG) is organized so that responders can find a material by:

Answer: The material's name (yellow pages), UN/NA number (orange pages), or placard type (white pages at the back)

The ERG has three primary lookup methods: the yellow-bordered index (alphabetical by material name), the orange-bordered index (numerical by UN/NA number), and the white pages in the back (for placard/label type). Each method leads to a numbered Guide page with emergency response information. The green pages list water-reactive and air-reactive materials.

At a hazmat incident, what does the term 'IDLH' mean, and why is it significant for firefighters?

Answer: Immediately Dangerous to Life and Health — it is the concentration at which exposure would cause irreversible harm or death within 30 minutes

IDLH stands for Immediately Dangerous to Life and Health. It is an OSHA-defined concentration threshold: exposure at or above IDLH could cause irreversible adverse health effects or impair the ability to escape (e.g., due to unconsciousness) within 30 minutes. IDLH values are used to determine when respiratory protection is mandatory and to establish safe entry requirements.