☣️ 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.
UN 3373 is Biological substance, category B, assigned to ERG Guide 158. First responders should verify the shipping papers and SDS, isolate the area, and base entry, PPE and control tactics on the product's listed hazards.
Hazard overview: The main hazard is potential infection from damaged packages or specimens. Prevent direct contact, aerosol generation, and environmental release.
Response guidance: For UN 3373, isolate damaged packages, avoid direct contact, prevent aerosol generation, use biohazard containment procedures, and notify public health or facility safety personnel.
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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 than Category B materials.
- 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
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.
| 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
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 the emergency response telephone number on the shipping paper, if available.
- 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 than Category B materials.
• Runoff from fire control or dilution water may cause environmental contamination.
— First Actions —
• CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Consult the shipping paper to identify the substance involved.
SOURCE: allfirefighter.com/hazmat/un/biological-substance-category-b-un-3373 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3373 Biological substance, category B Cls6 ERG158 | allfirefighter.com/hazmat/un/biological-substance-category-b-un-3373SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/biological-substance-category-b-un-3373
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Frequently Asked Questions about UN 3373
UN 3373 is Biological substance, category B. It is assigned to ERG Guide 158 for initial emergency response.
Yes, it is a Category B biological substance. Damaged packages should be handled as a potential infection exposure.
Use gloves, eye protection and protective clothing; add respiratory protection if aerosols could be generated.
Isolate the package, avoid direct contact, contain leaks, disinfect under approved procedures and notify safety or public health personnel.
The biological material itself is not normally flammable, but packaging or transport media may burn in a fire.
Avoid touching specimens, creating aerosols, spreading contaminated runoff or opening damaged packaging without proper controls.
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.