UN 1593 — Methylene chloride
Placard: Toxic. ERG Guide 160. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Methylene chloride, also known as dichloromethane, is a colorless, volatile liquid with a sweet, chloroform-like odor. It is classified as a DOT class 6 substance and is widely used in various industrial applications, including paint stripping, adhesive removal, and as a solvent. First responders may encounter methylene chloride in the event of a spill or leak during transportation or storage. The scale of production and transport of methylene chloride is significant, with millions of pounds being shipped annually. As a result, it is essential for emergency responders to be aware of the hazards associated with this substance and to have a plan in place for responding to incidents involving methylene chloride. Methylene chloride is also known by its synonyms, including DCM and methylene dichloride. The CAS number for methylene chloride is 75-09-2.
Hazard overview: Methylene chloride is toxic by ingestion and vapors may cause dizziness or asphyxiation, especially in closed or confined areas.
Response guidance: In the event of a methylene chloride spill or leak, it is essential to isolate the area immediately. The ERG recommends isolating the spill 25-50m in all directions, and for large spills, considering initial evacuation of 100m downwind. First responders should stay upwind, uphill, and/or upstream of the spill to minimize the risk of exposure. The correct suppression agent for methylene chloride is not typically required, as it is non-flammable, but water spray can be used for vapor knockdown. Decontamination is critical, and CHEMTREC should be contacted in the event of a large spill or leak. It is also important to note that methylene chloride is slightly soluble in water and has no significant reaction with water.
Firefighter training notes: First responders should be trained to respond to methylene chloride spills or leaks, with a focus on isolation, decontamination, and vapor knockdown. A common tactical error when responding to methylene chloride incidents is underestimating the risk of exposure and not wearing adequate PPE. ICS positions, such as the incident commander and safety officer, should be aware of the hazards associated with methylene chloride and ensure that first responders are properly trained and equipped to respond to incidents involving this substance. Mutual aid criteria should also be established to ensure that adequate resources are available to respond to large-scale incidents.
Regulatory context: Methylene chloride is classified as a DOT class 6 substance, which indicates that it is toxic and can cause serious health effects if not handled properly. The OSHA PEL for methylene chloride is 25 ppm, and the TLV is 50 ppm. Methylene chloride is not listed on the CERCLA list, but it is regulated by OSHA and the EPA.
Storage & handling: Methylene chloride should be stored in a well-ventilated area, away from incompatible materials such as strong oxidizers and alkalis. The temperature limit for storing methylene chloride is not well established, but it should be kept away from heat sources and ignition sources. The container type for storing methylene chloride should be compatible with the substance and should be designed to prevent leakage or spillage.
UN 1593 Quick Details
Common Hazards of UN 1593
- Toxic by ingestion.
- Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas.
- Exposure in an enclosed area may be very harmful.
- Contact may irritate or burn skin and eyes.
- Fire may produce irritating and/or toxic gases.
- Runoff from fire control or dilution water may cause environmental contamination.
- Some of these materials may burn, but none ignite readily.
- Most vapors are heavier than air.
Chemical Identity & Physical Properties
Methylene chloride is a colorless, volatile liquid with a sweet, chloroform-like odor. It has a boiling point of 40°C (104°F) and a vapor pressure of 47.4 kPa at 20°C. The specific gravity of methylene chloride is 1.33, which is denser than water. Methylene chloride is non-flammable under normal conditions and has a flash point that is not applicable.
| Also known as | DichloromethaneDCMMethylene dichlorideMethylene bichlorideMethane dichloride |
| CAS Number | 75-09-2 |
| Appearance | Colorless, volatile liquid with a sweet, chloroform-like odor. Denser than water and non-flammable under normal conditions. |
| Flash Point | Not applicable (non-flammable liquid) |
| Boiling Point | 40C (104F) |
| Vapor Density | 2.9 (heavier than air) |
| Water Reactivity | No significant reaction; slightly soluble in water |
Fireground Response Guidance — UN 1593
Extinguishing Media
PPE Requirements
The recommended PPE level for responding to a methylene chloride spill or leak is Level B, with a minimum requirement of SCBA and chemical-resistant gloves and suit. This is because methylene chloride can accumulate in low-lying areas and can cause serious health effects if inhaled or if it comes into contact with the skin. The use of SCBA is mandatory to prevent inhalation of methylene chloride vapors, and chemical-resistant gloves and suit are necessary to prevent skin contact.
Isolation & Evacuation
First Actions for a UN 1593 Incident
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 50 meters (150 feet) in all directions.
- Consider initial downwind evacuation for at least 100 meters (330 feet).
📋 Copy & Share Field Card
UN 1593 — Methylene chlorideUse 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.