Ammonia Leak on Night Shift With Ventilation Down

Ranked by 'protect people, then contain, then diagnose.'

1. Do not enter, and close the machine-room door behind you. 60 ppm and rising with no ventilation is a deteriorating atmosphere; the doorway is the boundary.
2. Activate the plant alarm and account for the twelve warehouse workers per the emergency plan - evacuation or shelter-in-place as the plan directs. People first.
3. Call the fire department and plant management as the plan requires, and state the reading, the suspected source, and that ventilation is down.
4. Try to restore ventilation from outside the room. Investigate the tripped breaker from the outside; reset it once with the door closed. If it trips again, leave it off and report it - a breaker that trips twice is a fault, not an inconvenience.
5. Shut the compressor down remotely if a remote stop exists. If the only stop is inside the room, do not enter to press it; wait for responders with SCBA.
6. Establish an exclusion zone and keep monitoring the detector from outside, logging readings and times so responders get a trend, not a single number.

Note what is not on the list: opening the door wide to 'air it out' (spreads vapor), and entering with the cartridge respirator.

Use SCBA for any entry. Do not use the cartridge respirator.

Justification:

• The reading of 60 ppm already exceeds the 50 ppm OSHA permissible exposure limit, and the trend is upward at about 5 ppm per ten minutes. The concentration at the time of entry is unknown and could be far higher than the last sample.
• Ammonia's IDLH is 300 ppm. Air-purifying cartridges are for low, known, stable concentrations with adequate oxygen - they provide no oxygen, no protection against an oxygen-deficient atmosphere inside the room, and their capacity is finite and unpredictable at rising concentrations.
• Cartridge respirators with ammonia cartridges are appropriate for escape from a low-level release, not for emergency entry or for diagnosing a live leak.
• Odor is not a gauge. Ammonia's odor threshold is well below 50 ppm, so the operator may smell it strongly at a concentration that is still low, or lose the ability to smell it after brief exposure.

Entry procedure: two-person minimum, SCBA with a standby outside on SCBA or with the means to rescue, communication, and a defined retreat. If the reading rises sharply or the plume enlarges, withdraw and let the fire department handle it.

Before re-entry without respiratory protection:

• The source is isolated (compressor stopped, suction and discharge valves closed, refrigerant pumped out of the seal area if possible).
• Mechanical ventilation is running and verified by airflow, not just by a starter that is 'on'.
• A calibrated direct-reading instrument shows the concentration below the plant's action level and falling, with the person testing from the doorway before stepping in.
• A standby person remains outside with communications, and the detector is watched for a rise during the entry.

Before returning the compressor to service:

• The shaft seal is repaired and the repair is leak-checked (pressure or vacuum test per procedure), not merely tightened.
• The ventilation interlock is proven by test - trip the detector and confirm the fan actually starts - and the tripped breaker's root cause is found and corrected.
• The ammonia detector is calibrated and its alarm setpoints verified.
• Oil level, oil pressure, and vibration are checked on a supervised restart, with a second person watching the seal area with a leak detector.
• The event, the readings, the actions, and the corrective work are documented in the plant log, with the emergency plan reviewed for what failed here (ventilation breaker, lone operator).