Understanding HEPA Filters and Air Purifiers

Air purifiers have become popular in Thailand, particularly since PM2.5 awareness increased. But with so many products on the market, understanding the filter grades matters.

Filter grades work on a scale. G4 is a pre-filter that catches large dust, hair, and particles. F7 is a mid-grade filter that captures finer dust and some pollen. H12 and H13 are HEPA grades that remove 99.5% and 99.95% of particles down to 0.3 microns respectively. This includes PM2.5, mold spores, bacteria, and most viruses.

For Thai conditions, H12 or H13 HEPA is the minimum you should look for. Combined with an activated carbon layer to absorb VOCs and formaldehyde (common in new furniture and building materials), you get comprehensive protection.

UV disinfection is an additional layer found in better units. UV-C light destroys the DNA of bacteria and viruses passing through the unit. It is particularly useful in medical settings, schools, and homes with vulnerable family members.

How often do filters need replacing? Under normal Bangkok conditions, pre-filters should be cleaned monthly. HEPA filters typically last 6 to 9 months. During haze season or high pollution periods, replacement may be needed sooner.

Sizing matters here too. An air purifier is rated by the room size it can handle. Running a small unit in a large room means it cannot cycle the air fast enough to be effective.