UN 2785 — Thiapentanal
Placard: Toxic. ERG Guide 152. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Thiapentanal is a toxic sulfur-containing aldehyde shipped as a liquid with a strong onion- or garlic-like odor. Treat vapor and liquid contact as significant exposure hazards.
Hazard overview: Thiapentanal is toxic and may be harmful or fatal by inhalation, ingestion or skin absorption. Vapors are irritating and can be noticeable at low levels because of the strong sulfur odor. The liquid is combustible and can give off flammable vapors when heated.
Response guidance: Isolate the release, keep personnel upwind and control ignition sources. Use SCBA and chemical-resistant clothing; apply foam, dry chemical, CO2 or water spray as directed by incident command.
Firefighter training notes: Train responders to identify the UN number, product name, placard, container type and exposure route before committing personnel to the hot zone.
Regulatory context: Use the proper DOT shipping description, ERG guide, SDS and site-specific response plan; do not substitute this summary for regulatory compliance.
Storage & handling: Store in tightly closed, compatible containers away from heat, ignition sources, drains and incompatible materials listed in the SDS.
UN 2785 Quick Details
Common Hazards of UN 2785
- Thiapentanal is toxic and may be harmful or fatal by inhalation, ingestion or skin absorption.
- Vapors are irritating and can be noticeable at low levels because of the strong sulfur odor.
- The liquid is combustible and can give off flammable vapors when heated.
- Fire may produce toxic sulfur oxides, carbon oxides and irritating smoke.
- Vapors are heavier than air and can collect in low or confined spaces.
- Skin or eye contact may cause irritation; prolonged contact increases absorption risk.
- Containers may rupture when heated.
- Contaminated runoff should be contained and treated as hazardous.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a strong onion-like or garlic-like odor at room temperature.
| Also known as | Thiapentanal3-(Methylthio)propionaldehyde3-(Methylthio)propanalMethional |
| CAS Number | 1003-10-7 |
| Appearance | Colorless to pale yellow liquid with a strong onion-like or garlic-like odor at room temperature. |
| Flash Point | 54°C (129°F) |
| Boiling Point | 105-106°C (221-223°F) |
| Vapor Density | 2.9 (heavier than air) |
| Water Reactivity | No significant reaction with water under normal conditions |
Fireground Response Guidance — UN 2785
Extinguishing Media
PPE Requirements
Level B minimum with SCBA; use full-face respirator and chemical-resistant gloves; avoid all skin contact due to high toxicity
Isolation & Evacuation
First Actions for a UN 2785 Incident
- Call 911 and the emergency response number shown on the shipping papers.
- Keep unauthorized personnel away and establish an initial isolation perimeter.
- Stay upwind, uphill and upstream; avoid low areas where vapors or runoff may collect.
- Avoid breathing vapors, dust, mist or smoke and prevent skin and eye contact.
- Do not touch damaged packages, leaking containers or spilled material without appropriate PPE.
- Eliminate ignition sources; stop traffic, engines, smoking and open flames if it can be done safely.
- Ventilate confined spaces only when responders are trained, equipped and monitoring conditions.
- Use ERG, SDS, shipping papers and air monitoring to set final isolation, evacuation and decon actions.
📋 Copy & Share Field Card
UN 2785 — ThiapentanalUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.