Has the time come for an essential part of your biosafety cabinet maintenance: replacing the filter? Here's a step by step guide to how:
(This specific article will only focus on Class II biosafety cabinets)
Before getting started, you should note that several things must be considered, and questions need to be asked, before a filter change takes place. These are as follows:
1. Is a qualified engineer doing the work? If not, this is highly recommended due to the nature of the risks involved.
2. Has the unit been thoroughly decontaminated using Vaporised Hydrogen Peroxide (VHP)? Decontamination is also known as fumigation.
3. Have you decided on a safe method of disposal for waste filters?
4. Has the power been switched off from the Biosafety Cabinet?
If the above four questions have been answered satisfactorily, then it is time to get into the method.
Step 1: Removing and Replacing The Exhaust HEPA Filter From The Biosafety Cabinet
To remove the exhaust HEPA filter, the frame surround at the top of the biosafety cabinet needs to be removed. Take care not to damage the airflow sensor that is positioned in the housing.
Removing Down flow HEPA Filter Frame
Once the housing is removed, the filter frame can be unbolted, and the HEPA/ULPA filter lifted out.
HEPA Filter Removal
You can then position the new filter, and perform the reverse process to fit it. It is important to make sure the filter frame bolts are tightened equally to ensure there is no warping of the frame, which could cause leaks.
Step 2: Removing and Replacing The Down flow HEPA Filter
Next, you remove the down flow HEPA filter from inside the working area.
Firstly, remove the UV light fitting (if you have it installed in your cabinet) and the down flow air sensor from the back wall. This allows for easier removal of the down flow filter.
Next, remove the stainless steel mesh cover from the roof of the work area. This is to protect the HEPA filter from any damage.
Then unbolt the HEPA filter frame taking care to have proper support for the filter frame as it is lowered into the work area.
Once the old filter is removed a new filter can be fitted to the frame and lifted back up into the ceiling of the unit. When the bolts are tightened, it is important to ensure these are drawn evenly, just like the down flow filter housing.
Step 3: Setting Up and Calibrating the New Filters
When the new filters are in place, it is vital to ensure that the cabinet is functioning correctly before use. An airflow calibration should take place as a first step. Following this, a DOP test to check the integrity of the new filters and the seals should be undertaken. Finally, a Ki-Discus test should be performed to ensure your Class II cabinet is maintaining containment in line with EN12469.
As with all biosafety cabinet maintenance, when all of the above has been completed, it's essential that the changes made and the tests carried out are documented correctly and added to the assets works register.
Typically filter changes should be carried out by a qualified testing and maintenance company that will validate and sign off on their work. That being said, if you have a facilities team in-house, you now know how to change a filter on a TION Class II BIsoafety Cabinet.