What is the Safe Filter Handling in NQ500 Hospital Grade Unit?

SAFE FILTER HANDLING
We have recently become aware of some technicians' concerns with the safe handling of the two prefilters used in the NQ units, specifically the NQ500.

These are the filters that will be in need of upkeep:
The 2" filter is replaced monthly or bi-monthly depending on the relative nature and amount of dirt where the unit is located.
The 4" filter is replaced every six months, which also depends on the amount of dirt in the room that the unit is used.

This filter change will also be dependent on the two inch filter schedule, how dirty it was, and how long it was run before changing.

The owners' manual spells out what the pressure gauge should read when the filters are ready for changing.

In response to the concern:
The first line of defense is that all these filters can have a anti microbial treatment to inhibit the growth of pathogens, when ordered from the factory.

The second line of defense is that the UVGI irradiation chamber is directly above these filters and shines through them so that the filters are being continually bathed in UVGI radiation. The lamps' irradiation power onto the farthest filter, is indeed reduced. However, this continual irradiation into this area, will bring the total UVGI killing power (residence time)close to the value found in the upper UVGI chamber, which has over 4 times what is needed to kill TB.

The third line of defense is dehydration. The droplet nuclei, if attached to the filter, will be dehydrated during a recommended cleansing time before service and therefore should not constitute a problem to the technician.

A basic room cleansing time is discussed in the CDC guidelines' Table S3.1. If the same scenario is used for the cleansing time of the NQ unit then the prefilters will also be cleansed or dehydrated.

The CDC table indicates the length of time a room must be subject to a clean air stream in order to become 99.9% clean. A room requiring to be 99.9% clean and has clean air circulating at 12 air changes, will need 35 minutes to reach that cleanliness level.

It is important to note that the mixing factor may change this length of time, if it is any greater than 1, which happens to be the value used for the NQ500 by various tests and agencies.

We do recommend that technicians follow the hospital S.O.P. for standard HVAC filter changes and bag them for protection from future recontamination. The CDC has not required "bag in/bag out" design as stated in, and eliminated from, the original 1994 CDC guideline proposal and has also stated that no evidence has been demonstrated for this need.

However, all air filters should be handled in the same manner as the HEPA filters. Hospital SOP must be followed.