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Emergency release devices for door latches - hazard alert

1 July 1994

Emergency release devices for door latches on cold rooms, walk-in freezers, strong rooms and similar rooms

This hazard alert is issued following a potentially life-threatening situation that arose when a PhD student became trapped in a walk-in -20°C freezer in a laboratory at the Clayton campus.

What happened

The student was working alone in her laboratory in the Microbiology building late one Friday evening. She entered the -20°C freezer room and the door to the room closed behind her. The door latch had only recently been changed from a magnetic to a positive action latch to keep the door firmly closed in order to minimise temperature loss and frost formation around the door frame. An emergency latch-release device is fitted to the door but when the student pushed the large, mushroom-head button on the back of the door to activate the device it failed to operate and the door remained closed, trapping her in the freezer.

There is a simple alarm bell which can be operated from inside the freezer. However, the bell can only attract attention in the laboratory directly outside the freezer and at the time of this incident there was no one else in the building to hear the bell and render assistance. There is a switch inside the freezer that can be used to shut down the refrigeration plant but with the door closed the temperature would rise very slowly, almost certainly too slowly to prevent the death of any person trapped inside.

Eventually the student was able to force the door open by repeatedly crashing against the door with her body. She escaped, shaken but otherwise unharmed. However, if the tension on the latch had been greater, or if the student had lacked the physical strength to force the door open, she would have faced prolonged exposure to -20°C. In all probability there would have been a fatal outcome.

While there is a lack of scientific data about human life-expectancy under conditions such as those in the freezer, the ISO Technical Report No. 11079, Evaluation of cold environments - Determination of required clothing insulation, provides some indicators about the seriousness of exposure to cold. For instance, the Report recommends a maximum exposure to -20°C of 30 minutes to 3.5 hours, subject to the level of activity, the wind factor and the insulation properties of the clothing being worn. The student was wearing only light clothing and would have felt the deleterious effects of the cold in a very short time.

Lessons learned

  1. The emergency latch-release device was not being regularly tested
  2. The alarm system was inadequate because it would only be of use if there was someone in the building within hearing distance
  3. As entrapment in the room could lead to death, the room should have been declared a `high hazard' area and appropriate entry restrictions put in place. Entry when alone in the building should not have been permitted
  4. Technical staff from the Microbiology department dismantled and checked the door release mechanism. A retaining circlip was missing from a sliding rod that is meant to strike against and disengage the door latch when the mushroom-head release button is pushed. Without the circlip to hold it in place the rod had dropped out of position, thereby rendering the emergency release mechanism inoperative

Remedies

The department modified the mechanism on this and other doors with the same release mechanism by fitting a retaining collar to the sliding rod to supplement the circlip. The following additional precautions have been taken or are under consideration:

  1. The door latches have been reset to reduce the effort required to push the door open
  2. Emergency instructions that include how to operate the emergency release devices have been prepared and are displayed inside the freezers and cold rooms
  3. The department is investigating the feasibility of having an alarm with direct access to the Gatehouse installed in rooms with positive action door latches. Telephones may be appropriate in some locations
  4. The emergency door releases are to be tested periodically to ensure they function correctly. This will include escape mechanisms that have a wing nut which must be removed to release the door latch

Recommendations

The Occupational Health and Safety Branch recommends that all departments with cold rooms, walk-in freezers, strong-rooms or similar rooms fitted with doors that could trap occupants if the door closes, give urgent attention to the operation of the doors and emergency release mechanisms. The preceding precautions should be adopted where applicable, but in addition, the following points should be checked:

  1. Ensure that each door can be opened and closed freely with the minimum of effort
  2. Identify the type of door latch fitted to each room. Magnetic hold-shut devices are normally easy to force open but if a positive latch is fitted the operation of the release mechanism should be checked. If the latch is one of the push-button type described above, the release mechanism should be dismantled and inspected. On the Clayton campus the Maintenance Department will check the release mechanisms on request. Please contact Mr. Geoff Brace, ext. 53003
  3. Review the practices followed by staff and students who use cold rooms, walk-in freezers, strong rooms, etc. and ensure their procedures are appropriate for the conditions and circumstances
  4. Identify and check periodically all safety devices, not just those associated with this type of room

There have not been any other incidents of this type recorded at Monash University, but there is no cause for complacency. I urge all departments to take prompt action on the items listed in this hazard alert and especially to check doors and latches and rectify any deficiencies without delay.

Further information

Please contact OH&S on: