Atmospheric Gas Testing - AGT

 


Atmospheric Gas Testing - AGT


Atmospheric Gas Testing - AGT


Excavation & Trenching Safety Guide Pictorial



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Confined space activities are life threatening and gas testing plays a vital role. Atmospheric gas testing(AGT) within confined spaces shall include, but not be limited to, testing for oxygen (O2), flammable mixtures (Lower Explosive Limit [LEL]) toxic gases (e.g., H2S), and carbon monoxide (CO).

 

When atmospheric gas tests shall be performed and immediately recorded:

ü  Prior to entry.

ü  After breaks or other interruptions in the work activities.

ü  If there is any reason to believe that conditions inside the confined space have changed.

ü  At periodic intervals (e.g., every 2 hours) as necessary to determine whether acceptable atmospheric conditions are being maintained during the course of the confined space entry.

Atmospheric gas tests shall only be conducted by a certified gas tester.


HEIGHT WORK | WORK AT HEIGHT DO'S


Mechanical Ventilation - Initial gas testing prior to entry shall be performed with all mechanical ventilation shut down at least 15 minutes prior to testing.

Unacceptable Levels - Initial entry shall be prohibited if gas testing indicates an oxygen deficiency or the presence of unacceptable levels of flammable (LEL) or toxic materials, etc., within the confined space. Only after purging with mechanical ventilation and/or cleanup has rendered the space free of hazardous concentrations (as verified by continuous gas testing inside the confined space) shall initial entry be allowed.

Additional gas testing (e.g., after breaks) shall be conducted with the ventilation system turned on to ensure that contaminants are being removed and that the ventilation system is not a source of contamination.

Personal Gas Monitors - Continuous gas testing (e.g., by use of personal gas monitors) shall be used if the atmosphere inside the confined space is subject to change or if confined space entry activities involve combustion (e.g., welding or torch cutting).


Electrical Work | Permit To Work (PTW) 

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Evacuation of Personnel - Whenever a hazardous atmosphere is detected, the confined space shall be evacuated of all personnel until corrective actions have been taken and it has been verified that the confined space is safe for reentry.

Welding/Torch Cutting - Hot work activity shall not be permitted if the atmosphere is above 0% of the LEL.

The following environments are required prior to entry into or work inside a confined space:

A. No atmosphere-supplying respirator is required if:

·       Oxygen (O2) concentration is at or above 20.0% and less than or equal to 23.5%.

·       Flammable/combustible mixtures are less than 5% of the LEL.

·       Carbon monoxide (CO) is less than 35 parts per million (ppm).

·       Hydrogen sulfide (H2S) is less than 10 ppm.

·       Other potential toxic gas concentrations are below their threshold limit value (TLV).


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B. An atmosphere-supplying respirator shall be continuously worn if:

Ø  O2 concentration is less than 20.0%.

Ø  Flammable/combustible mixtures are at or above 5% and less than 10% of the LEL.

Ø  CO concentration is at or above 35 ppm and less than 1,000 ppm.

Ø  H2S concentration is at or above 10 ppm and less than 100 ppm.

Ø  Other potential toxic gas concentrations are above their designated TLV and at or below their IDLH level.

C. Confined space entry is not permitted at concentrations above 23.5% O2, at or above 10% LEL, above 1,000 ppm CO, above 100 ppm H2S, or above the Immediately Dangerous to Life or Health (IDLH) of any other potential toxic gas.

 

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