Safety Tip 1 - Telecommunications Manhole Gas
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The following information is from the OSHA Telecommunications Standard (1910.268), specifically the section regarding manholes and unvented vaults.
Under this standard, the only test required prior to an employee entering a manhole is for combustible gas when continuous forced ventilation is provided. Additional testing for oxygen deficiency is required only when forced ventilation is not provided. There is no mention in the standard requiring testing for other gasses such as Carbon Monoxide or Hydrogen Sulfide. Normally therefore, the “Test, Purge, and Ventilate” routine utilized by the majority of Telco's would preclude any requirement for testing for gasses other than combustibles. If unusual conditions dictate otherwise however, tests for other gasses (such as Carbon Monoxide or Hydrogen Sulfide) would be appropriate.
Requirements prior to entering manholes and unvented vaults .
Before an employee enters a manhole, the following steps shall be taken:
The internal atmosphere shall be tested for combustible gas and, except when continuous forced ventilation is provided, the atmosphere shall also be tested for oxygen deficiency.
When unsafe conditions are detected by testing or other means, the work area shall be ventilated and otherwise made safe before entry.
An adequate continuous supply of air shall be provided while work is performed in manholes under any of the following conditions:
Where combustible or explosive gas vapors have been initially detected and subsequently reduced to a safe level by ventilation,
Where organic solvents are used in the work procedure,
Where open flame torches are used in the work procedure,
Where the manhole is located in that portion of a public right of way open to vehicular traffic and/or exposed to a seepage of gas or gases, or
Where a toxic gas or oxygen deficiency is found.
The requirements of paragraphs (o)(2)(i) and (ii) of this section do not apply to work in central office cable vaults that are adequately ventilated.
The requirements of paragraphs (o)(2)(i) and (ii) of this section apply to work in unvented vaults.
Joint power and telecommunication manholes . While work is being performed in a manhole occupied jointly by an electric utility and a telecommunication utility, an employee with basic first aid training shall be available in the immediate vicinity to render emergency assistance as may be required. The employee whose presence is required in the immediate vicinity for the purposes of rendering emergency assistance is not to be precluded from occasionally entering a manhole to provide assistance other than in an emergency. The requirement of this paragraph (o)(3) does not preclude a qualified employee, working alone, from entering for brief periods of time, a manhole where energized cables or equipment are in service, for the purpose of inspection, housekeeping, taking readings, or similar work if such work can be performed safely.
Ladders . Ladders shall be used to enter and exit manholes exceeding 4 feet in depth.
Flames . When open flames are used in manholes, the following precautions shall be taken to protect against the accumulation of combustible gas:
A test for combustible gas shall be made immediately before using the open flame device, and at least once per hour while using the device; and
a fuel tank (e.g., acetylene) may not be in the manhole unless in actual use.