☣️ UN 3373 • CLASS 6
UN 3373 — Biological substance, category B
Placard: Infectious Substance. ERG Guide 158. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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UN 3373 Quick Details
UN 3373
Product name: Biological substance, category B
DOT Class: 6
Placard type: Infectious Substance
ERG Guide: 158 (check current ERG)
Initial isolation: ERG 158: No specific isolation distances for Category B; containment and biohazard protocols per facility procedures; prevent environmental release of specimens
Common Hazards of UN 3373
- Inhalation or contact with substance may cause infection, disease or death.
- Category A Infectious Substances (UN2814, UN2900 or UN3549) are more hazardous, or are in a more
- Runoff from fire control or dilution water may cause environmental contamination.
- Damaged packages containing solid CO2 as a refrigerant may produce water or frost from condensation
- Contact with solid CO2 may cause burns, severe injury and/or frostbite.
- Some of these materials may burn, but none ignite readily.
- Some may be transported in flammable liquids.
Chemical Identity & Physical Properties
| Also known as | Diagnostic specimensClinical specimensBiological diagnostic specimensCategory B infectious substanceNon-infectious biological material |
| Appearance | Varies widely: typically liquid specimens (blood, urine, tissue samples) or solid biological materials in sealed containers at ambient temperature. May include cultures, patient specimens, or extracted samples. |
| Flash Point | Not applicable (biological material) |
| Boiling Point | Not applicable (biological material) |
| Vapor Density | Not applicable (biological material) |
| Water Reactivity | No significant reaction; biological specimens are typically in aqueous solutions |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3373
Extinguishing Media
Standard extinguishing agents acceptable; biological hazard containment takes priority over fire suppression method
PPE Requirements
⚠️ Level C minimum with nitrile gloves, eye protection, and respiratory protection if aerosol generation possible; avoid direct contact with specimens
Isolation & Evacuation
ERG 158: No specific isolation distances for Category B; containment and biohazard protocols per facility procedures; prevent environmental release of specimens
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 158).
First Actions for a UN 3373 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Consult the shipping paper to identify the substance involved.
- Isolate spill or leak area for at least 25 meters (75 feet) in all directions.
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📋 Copy & Share Field Card
UN 3373 — Biological substance, category BHAZMAT RADIO NOTE — UN 3373
Product: Biological substance, category B
Class 6 / Infectious Substance / ERG 158
PPE: Level C minimum with nitrile gloves, eye protection, and respiratory protection if aerosol generation possible; avoid direct contact with specimens
ISOLATION: ERG 158: No specific isolation distances for Category B; containment and biohazard protocols per facility procedures; prevent environmental release of specimens
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3373 — Biological substance, category B
Class: 6 | Placard: Infectious Substance | ERG Guide: 158
Appearance: Varies widely: typically liquid specimens (blood, urine, tissue samples) or solid biological materials in sealed containers at ambient temperature. May include cultures, patient specimens, or extracted samples.
Water Reactivity: No significant reaction; biological specimens are typically in aqueous solutions
Extinguishing: Standard extinguishing agents acceptable; biological hazard containment takes priority over fire suppression method
PPE: Level C minimum with nitrile gloves, eye protection, and respiratory protection if aerosol generation possible; avoid direct contact with specimens
Isolation: ERG 158: No specific isolation distances for Category B; containment and biohazard protocols per facility procedures; prevent environmental release of specimens
— Key Hazards —
• Inhalation or contact with substance may cause infection, disease or death.
• Category A Infectious Substances (UN2814, UN2900 or UN3549) are more hazardous, or are in a more
• Runoff from fire control or dilution water may cause environmental contamination.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Consult the shipping paper to identify the substance involved.
SOURCE: allfirefighter.com/hazmat/un/3373 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3373 Biological substance, category B Cls6 ERG158 | allfirefighter.com/hazmat/un/3373SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/3373
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Frequently Asked Questions about UN 3373
Inhalation or contact with substance may cause infection, disease or death. Category A Infectious Substances (UN2814, UN2900 or UN3549) are more hazardous, or are in a more Runoff from fire control or dilution water may cause environmental contamination. Damaged packages containing solid CO2 as a refrigerant may produce water or frost from condensation Contact with solid CO2 may cause burns, severe injury and/or frostbite. Some of these materials may burn, but none ignite readily. Some may be transported in flammable liquids.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level C minimum with nitrile gloves, eye protection, and respiratory protection if aerosol generation possible; avoid direct contact with specimens
Water reactivity: No significant reaction; biological specimens are typically in aqueous solutions. Recommended extinguishing: Standard extinguishing agents acceptable; biological hazard containment takes priority over fire suppression method.
ERG Guide 158 recommendation: ERG 158: No specific isolation distances for Category B; containment and biohazard protocols per facility procedures; prevent environmental release of specimens
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 158 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles.
This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.