Safety Cabinet ProcedureClifford Pemberton Ext: 6464 / 6488.

Safety Cabinet Fumigation Procedure

This procedure is for fumigating Class I and Class II safety cabinets using vaporised Formaldehyde, with or without an Ammonia neutralising solution.

Equipment required:Formaldehyde solution (37-41%), RO water, PVC tape, Scissors, UK/EU electrical plug adaptor, Ammonia solution (35%) & vaporising device (FAS2000 programmable evaporator/neutraliser or standard evaporator).

  1. Ensure the safety cabinet is clean, clear of materials (pipettes, Duran bottles, DispoSafes, etc) and safe to fumigate (not in use, no obvious damage).
  1. Clearly label the cabinet with “Fumigation in Progress” to ensure the process is undisturbed.
  1. Using a Fume Hood (not a Safety Cabinet); prepare a working dilution of the formaldehyde solution to ~20% (if using the combination evaporator/neutraliser) or ~14% (for standard evaporator without neutraliser). If ammonia neutralisation is being used; use the Fume Hood to prepare a working dilution of the ammonia solution ~11%.
  1. Place the vaporising device inside the Safety Cabinet to be fumigated and connect it to the electrical supply: This may require use of the UK/EU plug converted or an extension lead if there is no electrical supply point inside the cabinet.

If performing a formaldehyde-only fumigation (no neutralising solution) on a class II safety cabinet, without an external extraction system; the main vent on the cabinet needs to be connected to an external extraction point using fumigation tubing – this should be attached and screwed into place before the evaporator device is placed inside the safety cabinet.

  1. If using the FAS2000 programmable evaporator/neutraliser or similar device; turn the device on and program the vaporising run; fumigation requires six hours between the formaldehyde fumigation cycle and the ammonia neutralisation cycle. When programming the delay time make sure you give yourself sufficient time to secure the cabinet. Add the formaldehyde working solution to the fumigation well of the device (left, red on the FAS2000)& add the ammonia neutralising solution to the neutralising well (right, blue on the FAS2000). Start the fumigation cycle (press and hold ‘A’ and ‘OK’ on the FAS2000) and proceed to step 7.
  1. If using a standard, non-programmable evaporator device it needs to be carefully checked before adding the formaldehyde working solution: The device needs to be switched ‘on’ inside the Safety Cabinet but switched ‘off’ outside the Safety Cabinet. This is usually accomplished by connecting the device to the cabinet power supply, turning the unit on using the on/off switch and then switching off the Safety Cabinet power supply – this will enable you to begin the fumigation cycle remotely once the Safety Cabinet has been secured. Once the device is ready for remote activation; add the formaldehyde working solution to the well and proceed to step 7.
  1. Seal the Safety Cabinet with the vaporising device inside; close all panels tightly – including the night closure door normally used to work within the cabinet. If using an extension lead to connect the vaporising device to an external socket; close the cabinet as well as possible, leaving only a small gap for the lead. Many Class I Safety Cabinets have an access port built into the night closure door for this purpose.
  1. Once the Safety Cabinet has been sealed it must be secured to prevent vapour leakage: Use PVC tape to secure the edges of the night closure door, air vents, access panels on the outside of the cabinet and the outflow from the cabinet fans. Class II Safety Cabinets often have a HEPA- filtered outflow vent on the top or side of the cabinet and this must be sealed during fumigation.

Class I Safety Cabinets generally have a filtered extraction system built in, this should not be sealed but make sure that anyone that could be working near the far end is aware of the danger before the cabinet is vented (Estates or external engineers).

  1. If using a standard, non-programmable evaporator it can now be switched on remotely.
  1. Ensure that the fumigation cycle is proceeding correctly and that there are no leaks – this can be done by visual inspection (a white, steam-like condensation should form on the cabinet window) 10-15 minutes after the cycle begins. If you smell formaldehyde or notice any irritation of your eyes or nose; switch off the power supply to the vaporising device if safe to do so (usually accomplished by switching-off the cabinet) and evacuate the area; treat as a formaldehyde spill/leak and consult the relevant COSSH forms.
  1. The fumigation cycle will take at least six hours to complete. If using a programmable evaporator with a neutralising solution; allow a further two hours for the neutralisation cycle.
  1. After the fumigation (& neutralisation) cycle has been completed the cabinet can be vented: For class I safety cabinets this is as simple as turning on the extraction fan and running the cabinet as normal, while slowly removing the PVC tape seals and fully opening the night closure door. As above (step 10); if you notice any smell of formaldehyde or ammonia during the venting process, evacuate the area and treat as a spill.

Class II Safety Cabinets may or may not have an external extraction system; if the class II cabinet does have an external extractor it can be treated as a class I cabinet venting and you should proceed to step 14.

  1. If the cabinet does not have an external extractor the venting procedure will depend on the fumigation method used:

If a programmable evaporator with a neutralising solution has been used the PVC tape seals can be removed and the safety cabinet run normally, venting into the room.

If a formaldehyde-only fumigation has been carried out the cabinet should already be connected to an external extraction point (step 4); ensure the external extraction system is open and turned on, then run the cabinet normally and slowly remove the PVC tape seals. As above (step 10); if you notice any smell of formaldehyde or ammonia during the venting process, evacuate the area and treat as a spill.

  1. After the cabinet has been fumigated and vented; all internal surfaces will require cleaning – as will the evaporator device. Clean with 70% IMS; most surfaces will only need a quick wipe but there may be residues on some surfaces that may be harder to remove. The residues will normally be white or colourless but a quick wipe with Virkon will turn them yellow/ Cleaning with Virkon is fine but it should be followed with IMS to avoid rust formation.