Share this“How do I know when to change the filter in my isolator?”
This is a common question about isolators. We asked Frank Razzaboni of Park Bioservices, a designer and manufacturer of flexible front isolators/gloveboxes, surgical isolators, HEPA-filtered transport containers, and other biomedical equipment, to provide a few thoughts in response to these questions.
"Although not a direct measure of airflow, a Magnehelic gauge is the best practical indication of filter condition."
Filtration industry experts state that a filter should be changed when it reaches ½ its rated capacity—for example, if the CFM of the filter decreases from 40 CFM to 20 CFM. Once a filter is in place, however, it can be difficult to determine when it’s at the end of the useful life span.
A Magnehelic gauge is usually built into isolators, biological cabinets, and flume hoods to measure differential pressure. Although not a direct measure of airflow, it is the best practical indication of filter condition.
The best and easiest way is upon initial setup to set the Magnehelic gauge to .1” of water then to monitor the pressure on regular intervals (weekly at a minimum). If the isolator is running on positive pressure as particulate builds up and occludes (blocks) the media, it will climb in pressure.When the gauge reads .15” the filter should be changed. If the isolator is run on negative pressure, the gauge will decrease in pressure as it becomes blocked; when it reaches .05” the filter should be changed.
Mistakenly some technicians will move the ball gauge to increase or decrease flow to correct the setting to .1”—doing this then makes knowing the relative health of the filter difficult.
As an alternative to the procedure outlined above a second method can be performed by using a brand new reference filter. First, the used filter is removed. Next, the reference filter is put in its place and with the blower on the Magnehelic gauge set to .1”. The reference filter is removed. Next the old filter is reinstalled and the pressure is noted. If the pressure falls outside the proper range, (between .10-.15 for positive/ between .10 and .05 for negative) it should then be replaced.
It should be noted that although it is possible to change filters while in use in some cases it is always best to check and change filters between study groups.
Our thanks to Frank Razzaboni for taking the time to respond to this question. Park Bioservices LLC, 154 Center Street, Groveland, MA 01834; 800-947-5226; www.parkbio.com.