UN 1717 — Acetyl chloride

Acetyl chloride, UN 1717, is a highly flammable and toxic substance classified as a DOT Class 3 material. It is widely used in various industrial applications, including the manufacture of pharmaceuticals, dyes, and pesticides. First responders may encounter acetyl chloride during transportation accidents or industrial spills. The scale of production and transportation of acetyl chloride is significant, with thousands of tons being moved annually. As a result, it is essential for emergency responders to be aware of the hazards associated with this substance and take appropriate precautions. Acetyl chloride is a colorless to slightly yellow fuming liquid with a pungent, irritating odor.

Hazard overview: Acetyl chloride is highly flammable and toxic, posing a significant threat to human health and the environment. The substance can be easily ignited by heat, sparks, or flames, and vapors can form explosive mixtures with air. The vapor density of acetyl chloride is 2.7, which is heavier than air, making it a significant hazard in enclosed spaces. The LC50 value for acetyl chloride is not available, but it is known to be highly toxic. In the worst-case scenario, acetyl chloride can cause severe burns to skin and eyes, and prolonged exposure can lead to respiratory problems.

Response guidance: In case of an acetyl chloride spill, it is essential to isolate the area 50m in all directions and evacuate the immediate area if fire involves containers. First responders should wear Level B protective gear, including a chemical-resistant suit for splash protection, and a full face SCBA. The correct suppression agent for acetyl chloride is dry chemical, CO2, or dry sand, and alcohol-resistant foam may be used at a distance. No water jets should be used. Decontamination is critical, and CHEMTREC should be contacted immediately in case of a spill. It is also essential to ventilate closed spaces before entering and to stay upwind, uphill, and/or upstream of the spill.

Firefighter training notes: First responders should be trained to handle acetyl chloride spills and leaks. A critical competency requirement is the ability to identify the substance and take appropriate precautions. A known tactical error for this chemical class is the use of water directly on the spill, which can increase the risk of explosion and worsen the situation. ICS position needs include a hazardous materials team leader and a safety officer, and mutual aid criteria include the availability of Level B protective gear and CHEMTREC contact information.

Regulatory context: Acetyl chloride is classified as a DOT Class 3 material, and it is subject to the regulations of the Pipeline and Hazardous Materials Safety Administration (PHMSA). The OSHA PEL for acetyl chloride is not established, but the substance is listed on the CERCLA list of hazardous substances. The packing group for acetyl chloride is not available, but it is considered a highly flammable and toxic substance.

Storage & handling: Acetyl chloride should be stored in a cool, dry, well-ventilated area away from incompatible materials such as water and ignition sources. The temperature limit for storage is 20C (68F), and the substance should be kept away from heat sources and ignition sources. The top three incompatible materials for acetyl chloride are water, aluminum, and magnesium, and the ventilation standard for storage is a well-ventilated area with a minimum of 10 air changes per hour.