Fire & Explosion Prevention

Work where a flame may be produced should not normally be performed in a confined space, except in the following situations:

• All flammable gases, liquids, and vapors have been removed before the start of any hot work. Mechanical ventilation can be used for the following reasons:
  • To keep the concentration of any explosive or flammable hazardous substance lower than 10 percent of its Lower Explosive Limit.
  • To ensure that the oxygen content in the confined space is not enriched. The oxygen content of the air should be less than 23 percent but greater than 19.5 percent.
• Surfaces coated with combustible material have been cleaned or shielded to prevent ignition.
• The confined space contains no fuel or fuel containers.
• Welding equipment is in good condition.
• Spark-resistant tools are used.
• All equipment is bonded or grounded properly.

Employers must monitor the concentrations of oxygen and combustible materials whenever hot work takes place in a confined space, making certain that oxygen levels remain in the proper range. If this is not possible, employers must take additional precautions to ensure workers' safety before they enter the confined space.

If potential flammable atmosphere hazards are identified during initial testing, the air in the confined space should be cleaned or purged, ventilated, and then tested again before entry to the confined space is allowed. Entry should be allowed only after testing has confirmed that the atmosphere in the confined space is within allowable limits, as the gases used for purging can also be extremely hazardous.

To learn more about Confined Space Competent Person/Supervisor visit our Confined Space Competent Person/Supervisor Online Training web page.