UN 2693 — Bisulphites, aqueous solution, n.o.s.
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Bisulphites, aqueous solution, n.o.s. is a variable corrosive solution that may release sulfur dioxide. Concentration and additives must be confirmed from shipping papers and SDS.
Hazard overview: Bisulphites, aqueous solution, n.o.s. is a variable corrosive solution. Sulfur dioxide release is the key inhalation concern, especially if the product is heated or mixed with incompatible acids.
Response guidance: Isolate the spill, control downwind exposure and contain runoff. Use water spray or fog only from a safe distance for vapor reduction or exposure protection as SDS permits.
Firefighter training notes: Train crews to identify Bisulphites, aqueous solution, n.o.s. by UN number, placard, ERG guide and SDS before choosing entry, isolation or extinguishment tactics.
Regulatory context: Use UN 2693, ERG 154, SDS, container labels and shipping papers to confirm the exact hazard profile and protective action distances.
Storage & handling: Store in closed, compatible containers away from heat, ignition sources and incompatible materials; keep the area ventilated and protected from damage.
UN 2693 Quick Details
Common Hazards of UN 2693
- Corrosive solution; skin or eye contact can cause burns or severe irritation.
- May release sulfur dioxide, especially when heated, acidified or disturbed.
- Sulfur dioxide vapors can irritate eyes, throat and lungs and may collect downwind.
- Non-flammable solution, but fire exposure can release toxic corrosive gases.
- Runoff can be acidic or toxic and may contaminate waterways.
- Reaction severity depends on concentration and exact formulation.
- Containers heated by fire may rupture or vent.
Chemical Identity & Physical Properties
Clear to yellowish aqueous liquid with sharp sulfur dioxide odor and acidic pH.
| Also known as | Bisulfites aqueous solutionHydrogen sulfite solutionAcid sulfite solutionBisulphite liquorHSO3- solution |
| Appearance | Clear to yellowish aqueous solution with a pungent, sharp sulfur dioxide odor. Liquid at room temperature with acidic pH. |
| Flash Point | Not applicable (non-flammable aqueous solution) |
| Boiling Point | Approximately 100C (212F), similar to water depending on concentration |
| Vapor Density | Not applicable (aqueous solution; vapors if any are SO2) |
| Water Reactivity | Miscible with water; dilution or heating may release sulfur dioxide gas |
Fireground Response Guidance — UN 2693
Extinguishing Media
PPE Requirements
Use SCBA with chemical-resistant suit, gloves, boots and full face/eye protection when vapor or splash exposure is possible.
Isolation & Evacuation
First Actions for a UN 2693 Incident
- Call 911 and the emergency response number shown on shipping papers or container documents.
- 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, smoke or mist and prevent skin and eye contact.
- Do not touch damaged containers or spilled material without appropriate chemical PPE.
- Ventilate confined spaces only when personnel are trained, monitored and properly equipped.
- Use ERG guidance, SDS, shipping papers and air monitoring before committing crews.
📋 Copy & Share Field Card
UN 2693 — Bisulphites, aqueous solution, n.o.s.Use 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.