Analyze an SDS

DOT Division 4.2: Spontaneously Combustible Materials

Division 4.2 is the DOT division for spontaneously combustible materials: pyrophoric materials that ignite within about five minutes of contact with air, and self-heating materials that can heat up and ignite in air without an external energy source.

How it is defined

  • Pyrophoric liquids and solids are the most hazardous, assigned packing group I.
  • Self-heating materials warm up in air, usually in larger quantities, and can ignite after a delay.
  • Many 4.2 materials must be kept under an inert gas or oil, or in sealed containers.

Summary of 49 CFR Parts 171 to 180. The regulations and the Hazardous Materials Table (49 CFR 172.101) control any shipment.

Label and placard

Colors
White upper half, red lower half
Symbol
Flame

A diamond that is white on the top half and red on the bottom half, with a flame and the number 4.

Packing groups

PG I for pyrophoric materials; PG II and III for self-heating materials of decreasing hazard. How packing groups work.

Common examples

  • White phosphorus
  • tert-Butyllithium and other pyrophoric reagents
  • Some finely divided metal powders
  • Oily rags in some conditions (self-heating hazard)

How it relates to GHS

Corresponds to GHS pyrophoric liquids, pyrophoric solids and self-heating substances.

DOT classes and GHS classes are assigned under different rules, so a product can have different severity labels in each. See also all GHS hazard classes.

Safe handling reminders

  • Handle under inert atmosphere as the SDS directs.
  • Store sealed in an appropriate cabinet.
  • Know the correct extinguishing media; water is wrong for many pyrophoric metals.

Where to find it on an SDS

Section 14 shows Division 4.2, UN number, packing group and the ERG guide number. Look in Section 14: Transport information. Hazard classification for the workplace is in Section 2. You can also see how a UN number points to a response guide on the UN and NA numbers page.

Frequently asked questions

What is a Division 4.2 material?

A Division 4.2 material is spontaneously combustible: it either ignites on contact with air (pyrophoric) or heats up and ignites in air without an external ignition source (self-heating).

General reference only. It does not replace the supplier's SDS or the current federal regulations.