21 JANUARY 2003
fuel sludge and displaced vapor in a way that will reduce the possibility of any hazardous condition
(toxicity, asphyxiation, fire, explosion) inside the tank and in the surrounding area.
11.11.5. Ensure eductor-type air-movers have been operating continuously until the tank is safe to
enter. Operate eductors for at least one hour or until LEL and oxygen are within safe limits
immediately prior to entrants entering the tank and throughout the operation to maintain a safe
11.11.6. Everyone entering must wear an approved supplied air respirator (SAR) with emergency-
egress SCBA until the tank is declared hazard-free as specified in AFOSH Std 48-137,
11.11.7. All tanks being cleaned or repaired must be considered explosive until all sludge and loosely
adhering rust and scale has been removed, regardless of the type of stored fuel.
11.11.8. All tanks being cleaned or repaired must be considered leaded unless positive proof exists
that the tank has never contained leaded fuel, or the tank has been coated using the Air Force standard
epoxy tank-coating system and has not held leaded fuel since. Before tank entry is authorized
without PPE, the LEL reading must be zero, oxygen levels between 19.5% and 23.5%, and lead,
benzene, and other toxic material levels within safe limits. Refer to API Standard 2015 for additional
11.12. Atmospheric Testing.
11.12.1. Temporarily stop ventilation and perform vapor testing from outside the tank. Test the
interior of the space by extending a hose and sample probe within 152 millimeters (6 inches) of the
Repeat every fifteen minutes for the duration of the operation.
AFOSH Std 91-25, Paragraph 3.3.8, for testing sequence. Workers may enter the tank when vapor
levels are below 10% of LEL if they are equipped with approved SAR with emergency SCBA. Never
enter a tank without proper respiratory protection unless the LEL is zero, the oxygen level is within
tolerances (19.5% to 23.5%), and the BEE has determined that airborne benzene and other toxic
vapors are within permissible exposure limits.
11.12.2. Vapors will be present as long as fuel, scale, or sludge are inside the tank. Operate air
eductors continuously until all these materials have been removed.
11.12.3. Noisy units may be shut down while workers are in the tank if they impair the ability of
attendants to communicate with entrants.
11.12.4. Do not work within the tank until the vapor readings are below 10% LEL. If entry is
required when the LEL is above 10%, the TES will follow the procedures outlined in
AFOSH Std 91-25, Paragraph 6, and notify the command fuels engineer. The TES, with the
installation confined space program team (CSPT), will confirm whether the entry is permissible under
11.12.5. Reasons for not being able to get vapor readings below the 10% LEL, or in some cases
below 20% LEL, are:
22.214.171.124. Insufficient time to reduce vapor concentrations (which in turn can affect base mission
requirements and maintenance costs).
126.96.36.199. The size and type of tank and the amount of fuel and solid sludge to be removed.