TM 5-4220-231-14&P Table   2-2.    Operator     Preventive    Maintenance Checks    and   Services    For  Chamber    Operations - (Con't). B-Before D-During A-After W-Weekly ITEM INTERVAL ITEM   TO   BE   INSPECTED. Equipment Is NO Not   Ready/ B D A W PROCEDURE Available If: 4 0 0 Valves (4). Check all  valve    control knobs     for Valve    knob     is operability. Turn    each knob     counterclockwise to missing, the    open position, and    then    turn    it clockwise to broken or the   closed position. Replace control knob     if valve missing or   broken. operation is jammed, excessively tight,    or loose. WARNING Extreme care     must be   exercised when handling pressure gages. Failure    to   keep     gages free    of oil,  grease, and     rust    may    cause damage or inaccurate readings. Failure     to   observe this warning may    result     in  equipment failure, injury, or   death to   personnel. 5 0 0 Gages (5). Inspect for   damaged pointers, Lens     is cracked or   broken lens,    missing or   unseated missing or retaining ring,    or   other    visible     damage. Replace broken. if damaged. Needle pointer is damaged or not   adjusted to   0   psig. 0 0 Ensure pointer is  set    to   0  psig. Adjust     as required . 0 Monitor gages to   ensure proper pressure ranges Sudden drop during operation. in   pressure affects chamber operations (EXECUTE EMERGENCY PROCE- DURES, para. 2-10). 2-31