Defro DRX / OPTI V filters
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OriginalExtract filter size: 445x171x48 mmSupply filter size: 445x171x48 mmFilter class (EN779): M5+M5(AC)Filter quantity in a set: 2 filtersProtection levelFilter protection level indicates efficiency in blocking particles or contaminants, varying by standard and application.
BasicGeneral dust and particle filtration
Odours and smokeFilters out smoke and unpleasant smells
Pollen and moldCaptures pollen, mold spores, and other allergens
OriginalExtract filter size: 445x171x48 mmSupply filter size: 445x171x48 mmFilter class (EN779): M5+M5Filter quantity in a set: 2 filtersProtection levelFilter protection level indicates efficiency in blocking particles or contaminants, varying by standard and application.
BasicGeneral dust and particle filtration
Pollen and moldCaptures pollen, mold spores, and other allergens
House brandExtract filter size: 445x171x48 mmSupply filter size: 445x171x48 mmFilter class (EN779): M5+M5Filter quantity in a set: 2 filtersProtection levelFilter protection level indicates efficiency in blocking particles or contaminants, varying by standard and application.
BasicGeneral dust and particle filtration
Pollen and moldCaptures pollen, mold spores, and other allergens
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We’ve gathered answers to the most common questions about our products and services. If you can’t find an answer here, please contact us directly.
What filter type does a Defro DRX V or OPTI V unit use?
Defro DRX V and OPTI V units use an M5+M5 filter set — one M5 filter on the extract side to protect the heat exchanger and one on the supply side. We stock it as an original set and as a lower-cost house brand set, plus an original set with an activated carbon filter for odour control.
Can Defro filters be replaced without a technician?
Yes. The filters in Defro DRX V and OPTI V units sit behind the filter cover and slide out without tools, so you can change them yourself in a few minutes. Switch the unit off before opening the cover and check the airflow arrows on the new filters before inserting them.
Does Defro make ventilation units, or only heating systems?
Defro is best known for biomass boilers, but it also makes residential ventilation units with heat recovery, often installed alongside Defro heating equipment. We stock filter sets for the Defro DRX V and OPTI V units, which share the same filter size.
Can I order a full year’s supply of Defro filters at once, and is there a discount for doing so?
Yes — ordering a full year's worth of Defro filters (typically two to four sets, depending on your replacement interval) in one purchase is a convenient way to avoid running low, and multi-set orders are usually priced lower per filter than buying one set at a time.
Since Defro units are often installed alongside biomass heating, is an activated carbon filter option available to manage smoke odour?
Yes. We stock an original Defro DRX V / OPTI V activated carbon set (M5+M5 AC). The carbon layer helps absorb smoke and other odours drawn into the fresh-air intake — for example from a nearby wood burner or biomass boiler — while still filtering dust at M5 level. It replaces the standard set and fits in the same two slots.
Our Defro unit is in a house with a wood stove — does that change which filter we should use?
It makes the choice of filter more important, not less. In homes with a wood stove or pellet boiler — and in neighbourhoods where many houses heat with wood — the outdoor air carries considerably more fine soot and smoke odour through the winter. Defro DRX V and OPTI V units use an M5+M5 filter set; change it more often during the heating season from October to March, as soot loads the filters faster. If smoke odour is the main problem, the original activated carbon set (M5+M5 AC) replaces the standard set in the same two slots and still filters dust at M5 level. Switch the unit off before opening the filter cover.
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