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.
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.
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.