Protect your HEPA. Keep airflow strong.
- OEM 3M Filtrete pre‑filter for the XJ‑2 negative‑pressure HEPA unit—part #41144.
- Rated 80–85% ASHRAE efficient to capture larger particles before the HEPA, extending service life.
- Change when the gauge says so: use the XJ‑2’s Minihelic® pressure gauge or noticeable airflow drop to know it’s time.
The 3M Filtrete prefilter protects the HEPA filter and is 80-85% ASHRAE Efficient
Dirty air passes through the prefilter. The prefilter removes large particulate. The primary filter then captures the remaining particulate. As the contaminant load on the filters increases, the filters become more efficient in capturing the smaller particles. At the same time, however, the dirty filter allows less air to pass through resulting in less particle collection and a decrease in the overall effectiveness of the air cleaner.
The XJ-2 air cleaner is equipped with a pressure gauge which indicates the restriction to airflow caused by the filters loading with particulate. When the air filter gauge reaches the red arrow or a noticeable reduction in airflow occurs, it is time to clean or replace the prefilter and possibly the primary filter. The CDC guidelines specify that the HEPA filter shall be replaced every six months.
Key Benefits
- Captures larger particles before the HEPA filter
- Helps extend HEPA filter service life
- Maintains consistent airflow and system efficiency
- Supports cleaner operation in dusty environments
- Genuine 3M™ Filtrete™ filtration media






