Hazmat Awareness · Chapter 6 · Review · Awareness track

Hazard Assessment and Risk Evaluation

Referencing the content of hazardous materials awareness and operations at the awareness level

Risk-based size-up balances weather, container, population, and information quality; when uncertain, stay defensive.

Learning objectives (6)

Sketch control zones — Describe hot, warm, and cold areas on a map for command even if not operating inside.
Perform risk-based size-up — Weigh likelihood and consequence before upgrading response mode.
Identify worst-case scenario — Maximum credible release for planning perimeters when data are missing.
Hold defensive when uncertain — Do not commit entry teams until hazards and resources are clear.
Use population risk — Consider vulnerable populations downwind in protective action decisions.
Document size-up factors — Record wind, container, placards, and patient count for ICS.

Chapter outline

Weather and terrain effects
Container stress and breach indicators
Population and exposure risk
Worst-case vs most likely case terms
Hot, warm, cold zone sketch
EPA safety zone language
Limited information hold defensive
ICS map sketch for command briefing

When sources disagree (9 topics to verify before you teach from this chapter alone)

Printable study sheet Printable study sheetRead first, then practise the track.

Showing Awareness track material. Switch tracks on the chapter page.

Vocabulary · 14

size-up
Continuous assessment of hazard, exposures, and response needs.
SourceFEMA — National Incident Management System (NIMS) (FEMA). Retrieved 2026-05-21: https://www.fema.gov/emergency-managers/nims
risk assessment
Evaluation of probability and severity of harm.
SourceEPA emergency response — safety zones (hot, warm, cold) (U.S. Environmental Protection Agency). Retrieved 2026-05-21: https://www.epa.gov/emergency-response/safety-zones
worst case
Maximum reasonable release for planning.
SourceEmergency Response Guidebook (ERG) 2024 (U.S. DOT / PHMSA). Retrieved 2026-05-21: https://www.phmsa.dot.gov/hazmat/erg/emergency-response-guidebook-erg
most likely case
Reasonable expectation based on current conditions.
SourceNFPA 470, Standard for Hazardous Materials/Weapons of Mass Destruction (NFPA). Retrieved 2026-05-21: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=470
downwind
Direction vapor travels relative to wind.
SourceNOAA CAMEO — ERG protective action distance background (NOAA Office of Response and Restoration). Retrieved 2026-05-21: https://cameochemicals.noaa.gov/help/erg/erg_distances.htm
terrain channeling
Valleys and streets concentrate vapor flow.
SourceNOAA CAMEO — ERG protective action distance background (NOAA Office of Response and Restoration). Retrieved 2026-05-21: https://cameochemicals.noaa.gov/help/erg/erg_distances.htm
container breach
Loss of integrity leaking product.
Source49 CFR Subchapter C — Hazardous materials regulations (U.S. DOT / eCFR). Retrieved 2026-05-21: https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-C
BLEVE
Boiling liquid expanding vapor explosion risk on pressurized tanks.
SourceNIOSH Pocket Guide to Chemical Hazards (CDC / NIOSH). Retrieved 2026-05-21: https://www.cdc.gov/niosh/npg/
exclusion zone
Area where entry is prohibited.
SourceEPA emergency response — safety zones (hot, warm, cold) (U.S. Environmental Protection Agency). Retrieved 2026-05-21: https://www.epa.gov/emergency-response/safety-zones
vulnerable population
Schools, hospitals, crowds in protective action path.
SourceNOAA CAMEO — ERG protective action distance background (NOAA Office of Response and Restoration). Retrieved 2026-05-21: https://cameochemicals.noaa.gov/help/erg/erg_distances.htm
defensive hold
Maintain perimeter until better information arrives.
SourceNFPA 470, Standard for Hazardous Materials/Weapons of Mass Destruction (NFPA). Retrieved 2026-05-21: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=470
safety officer
ICS position monitoring hazards and PPE compliance.
SourceFEMA — National Incident Management System (NIMS) (FEMA). Retrieved 2026-05-21: https://www.fema.gov/emergency-managers/nims
branch
ICS organizational level for divisions of a section.
SourceFEMA — National Incident Management System (NIMS) (FEMA). Retrieved 2026-05-21: https://www.fema.gov/emergency-managers/nims
division
Geographic or functional ICS assignment.
SourceFEMA — National Incident Management System (NIMS) (FEMA). Retrieved 2026-05-21: https://www.fema.gov/emergency-managers/nims

Sequences · 2

Hazard Assessment and Risk Evaluation — Put these awareness-level steps in a logical order.
Learning objectives — Order these chapter objectives from first recognition steps toward notification and handoff.