How do I find a filter for a Venmar air purifier with HEPA filter?
...HRV clean and running efficiently, and if you need to replace it this page may help - How to choose between an HRV and ERV for home ventilation. Best of luck, we hope you can resolve this and regain your health.
Also, to discover if Air Purifiers with Hepa filters work, read the definitive Guide to cleaner indoor air.