Recently we have had a couple of Neg air units come in for decontamination and DOP testing. These items have been found to have dust particles in the rear or clean end of the unit. This end houses the motor and electronics. It is also the back end of the main filter which filters to 99.998% efficiency. No dust should be entering this area otherwise contamination into the environment or other rooms may occur. I have attached a photo showing how a unit should be set up.
1. The only part of the machine that should be exposed to the dirty room is the face of the unit which has the taped in pleat filter. This filter should be installed in the up and down pleat formation.
2. The unit should be taped against the virgin 200 micron polythene. No gaps should be present as this unit will pull the air towards itself.
3. You can install a roving head or slinky as some may call it onto the exhaust end to doubly ensure the air is filtered to the outside. If you maintain your equipment then you can exhaust into a clean room. The air from the exhaust unit is or should be cleaner than the air you breath normally.
4. On completion of your work,remove the tape from the polythene surround and place the transit cover (clear perspex) over the filter and lock in with supplied bolts. Don’t over tight. Don’t change the filter until the next job. Put the flap of the polythene back in place and tape securely to prevent possible leakage.
5. Change your disposable filter at the next job as this is your new work place and you shouldn’t have to worry about contamination, as you will be removing that during your work processes.
6. IT IS VITALLY IMPORTANT TO MINIMISE THE DUST DISTURBANCE INSIDE THE ENCLOSURE. That is why the unit should be outside the enclosure with dust movement limited to transiting to the NPUs for processing. I know vacuums create exhaust during work however that is part of the clean up anyway and should be blown side ways. It also doesn’t have the power of the NPU.
7. When you are working in your enclosure with your POSITIVE AIR RESPIRATOR, you should always face towards the NPU. This is so you don’t pull air and dust into you hood area and consequently your hair. Can you imagine decontaminating your hair. Also if the dust is pulling into your hair then it will be contaminating your body as well. If this is the case then you need to have a full shower decontamination unit in place.
In the photo you can see the clear polythene, the tape and the flap cut into the enclosure. Next to that we have an Air monitor which provides real time controls ensuring the work space is always under negative pressure.
Finally you may wander who is controlling these devices. Simple, its the COC. That person must be available to adopt an overview of the project, its progress, compliance issues and be available for inductions, emergencies and provide immediate assistance to staff.
Thats my opinion anyway.
Manuals in download page.