#78 Confined Spaces

Confined spaces can include tanks, silos, pits, vaults, pipelines, manholes, digesters, etc. But there are many other restrictive areas that qualify as well. A “Confined Space” is defined as a space which has any on of the following characteristics:

  • It has limited openings for entry and exit
  • It has unfavorable natural ventilation
  • It is not designed for continuous worker occupancy

Hazardous atmospheres in confined spaces present one of the greatest dangers to workers. Oxygen deficient atmospheres have less that 19.5% available oxygen. Do not enter an atmosphere with less that 19.5% oxygen without an approved, self-contained breathing apparatus! Flammable atmospheres contain two things that make them flammable: the oxygen in the air plus a flammable gas, vapor, or dust in the proper mixture. Toxic materials stored or used in the confined space, or in adjacent areas, can create toxic atmospheres. Ventilate with a blower or fan to remove harmful gases and vapors if necessary. The atmosphere of any confined space should be tested by a competent person before each shift or before any worker enters the space. Any power sources in the confined space which could present a hazard should be isolated and locked out. You may need to lock our electrical power, blank and bleed pneumatic and hydraulic lines, disconnect belt and chain drives and mechanical linkages on shaft-driven equipment, and secure mechanical moving parts within the confined space with latches, chains, chocks, blocks or other devices.


A standby person should be assigned to remain on the outside of the confined space and be in contact with the workers inside, either visually or verbally. The standby person should not have any other responsibilities and be able to call for immediate assistance in case of an emergency.