What are the Hazards Involved in Entering and Working in Confined Spaces?

2. FLAMMABLE ATMOSPHERES

Two things make an atmosphere flammable:

1. The oxygen in air, and
2. A flammable gas, vapor, or dust in the proper mixture.

Different gases have different flammable ranges. If a source of ignition (e.g., a sparking or electrical tool, static electricity, sand blasting) is introduced into a space containing a flammable atmosphere, an explosion will result.

An oxygen-enriched atmosphere (above 22%) will cause flammable materials, such as clothing and hair, to burn violently when ignited. Therefore, never use pure oxygen to ventilate a confined space. Ventilate with normal air.