Solid Concrete Walls

Confined Space Safety

By Ethan Davis

Confined Space – A confined space is any enclosure that is not designed for normal occupancy by humans, contains an actual or potential safety and/or health hazard, and restricts egress to such an extent that personnel would have difficulty escaping in the event of an emergency. Examples of spaces fitting this description include: animal confinement pits, storage tanks and bins, air handling units, piping, boilers, ducts, vaults, trenches, and manholes.

No authorization is to be given for entry into confined spaces that are considered immediately dangerous to life and health or where the potential exists for the generation of such. Examples of a confined space include:

(1) An area where there is potential of a non-respiratory atmosphere.

(2) An area where there is potential of an engulfment by loose particles or liquids.

(3) An area where there is potential of an explosive, flammable or toxic atmosphere.

(4) An area where an entrance and/or exit is restricted (limited access or egress).

(5) An area where welding, cutting, burning, painting, chemical handling, or any type of work which would create a toxin or non-respiratory atmosphere constitutes a confined space.

Entry Permit – The confined space entry permit provides a checklist of pre-entry precautions that must be taken. Documentation of monitoring and authorization of entry should be provided by the Manager or the Department Supervisor. A copy of the permit should be conspicuously posted at the site of entry. The permit should contain a record of the date of entry, monitoring requirements, relative location of entry and a description of the work to be performed. Permits are issued for 8-hour shifts only and must be reevaluated before each new shift begins working.

Site Contact Person – The superintendent, foreman, or other assigned employee who is the main contact person on the site and who is responsible for the compliance with these rules.

Operating Procedures

a. Determine any unusual conditions which may require special procedures unique to the area or task to be conducted (i.e., welding).

b. Purge, drain and/or evacuate process materials, chemicals and air.

c. Isolate the confined space from all external piping, process systems, affluent systems, utilities, and ducts that could cause materials to enter the confined space. This can be accomplished by inserting blanks and skillets, disconnection and capping of lines, double blocking and bleeding valves and/or physical disconnection of equipment.

d. Immobilize all mechanical services such as agitators, mixer paddles, fan blades, etc., through recognized lockout procedures and/or through physical disconnection of the drive mechanism from the power source.

e. If an assessment (testing) of the atmosphere indicates contamination is present, the cause/source of the contamination must be determined. Furthermore, it must be determined if contamination will increase during entry. Testing should include:

(1) Oxygen Atmosphere Testing: Testing should be done with a calibrated direct-reading oxygen indicator. The oxygen should contain at least 19.5% but less than 23.5% oxygen by volume. Measurements should be taken at the top and bottom of the space. Measurements should be taken every 15 minutes by the attendant. Tests must be repeated after a stoppage exceeding 30 minutes. Results should be documented in the permit. Entry is not permitted if the oxygen level is less than 19.5% or greater than 23.5%.

(2) Lower Explosive Level (LEL): Potentially explosive vapors and dust should be at 10% below the lower explosive level before personnel may enter the proposed work area, ensuring the appropriate PPE is being worn.

(3) Toxic Atmosphere Testing: If it is determined that any of the following toxins: Tolulene, Isopropyl Alcohol, or any material that is capable of generating any material that has a ceiling PEL (Permissible Exposure Limit) or LEL (Lower Explosive Level) were previously contained in the space, testing with color detection tubes (i.e. Dragger tubes), chlorine detector, or the Bio-systems Detector should be conducted. If atmospheric contamination exceeds 10% of the PEL, the space should be ventilated until the level is below 10%. The Manager or the Department Supervisor should be contacted if the contamination is IDLH (Immediately Dangerous to Life or Health). Entry is not permitted, except for emergency procedures approved by the Manager or the Department Supervisor, if toxic gases at an IDLH level exist. Measurements should be taken every 15 minutes by the attendant.

(4) Flammable Atmosphere Testing: If the space previously contained or currently contains flammable vapors, testing with a combustible gas indicator to determine the concentration of flammable gases and vapors must be conducted. If the concentration of flammable gas or vapor exceeds 5% of the lower flammability limit, the space should be ventilated until the concentration is below 5%. Entry is not permitted if the concentration exceeds 5%. Measurements should be taken every 15 minutes by the attendant.