Zehnder Filters

The fastest and most accurate way is to check the exact ComfoAir model code on the sticker on the unit's front panel: models 160, 180 and 200 are more compact and common in flats, while the 350, 375 (ERV), 550 and Q series (Q350, Q450, Q600) are higher-performance and more common in houses. If there's no sticker or it's been peeled off, simply remove the existing filter and measure its width, height and thickness — this lets you find an accurate match even without knowing the model name.

The filter class depends on the specific model's size:

• ComfoAir 160/180/200 — two G4-class filters, for both supply and extract air
• ComfoAir 350/375/550 and the Q series (Q350/Q450/Q600) — a G4-class filter for extract air and an F7 (ePM1) class filter for supply air

The F7 class captures fine particles, including pollen, which is why many households with allergy sufferers choose not to swap it for a cheaper option, even if the unit allows a lower class.

Because the F7-class supply-air filter is specifically designed to capture fine airborne particles, including pollen, it fills up faster in spring and early summer than during the rest of the year. Even while keeping to the standard 3–6 month replacement interval, it's worth visually checking the filter's condition monthly during pollen season — this helps maintain stable airflow and prevents allergy symptoms from worsening indoors.

No — filter dimensions in the Q series change along with the model number, so the Q350 uses a different size filter than the Q450 or Q600, even though all three follow the same G4/F7 filtration logic. Always check your exact Q model on the front panel before ordering, rather than assuming sizes are the same across the series — a filter of the wrong size simply won't fit the housing.

Both original and correctly chosen compatible filters work equally effectively, provided the filter class (G4 or F7) and exact dimensions match — both types are made to the same ISO 16890 standard. When ordering online, the most important thing is to check your ComfoAir or Q model code in advance so the filter is delivered without errors. Compatible filters are typically noticeably cheaper than original Zehnder products, which is why many buyers choose them as a more economical yet equally effective alternative.