Attach a HEPA filter to the HVAC outlet


I am currently living in China and want to improve the indoor air-quality. We have a Hitachi R410A HVAC. All the room in the house are controlled separately. Just to make it clear up front, I am not a technical guy and have no idea about air conditioning or HVAC (just learned what a HVAC is recently while doing some research into my issue).

The air is 'fresh' from outside. Since the Pm2.5 count is very high outside, I would like to filter the air that is blown in. I was thinking of a very straightforward solution, but I am not sure if it is possible. I want to buy some HEPA filters and cut them to the right size and fix these before the A/C outlets.

Will this work? Or does someone expect the pressure drop will be too high and create malfunctions or breakdown of the HVAC?

Thanks for the replies! As requested, I added some pictures of the unit that is placed outside (pic 1 and 2), example of the vents where the air from the room is sucked in an goes to outside (pic 3) and some of the vents were the air is blown in to the room (pic 4). Each room has its own set of vents. The HVAC is central and each room can be controlled separately with a controller on the wall.

HVAC unit outside the balcony

Type of HVAC

air out vents living room

air in vents on top living room

Also attached a link to the unit that we have (Hitachi multi set free, R410A, FSNQ) link to product Technical data brochure In the brochure I nowhere find any mentioneing of HEPA filters, so I guess these are not present.

Any more suggestions, thoughts about if it would be possible the attach a HEPA filter (need to think how without causing to much leakage) without causing serious HVAC malfunctioning would be appreciated.

Best Answer

Adding a filter onto an HVAC unit that's not designed for one will almost certainly cause problems... definitely with efficiency, possibly mechanical problems as well. If your model does not have a built-in filter you would probably be better served by getting a standalone air filter.

However, many units do have at least a basic filter built-in, and you may be able to clean it or replace it. Typically they are on the input side of the unit, to remove any particles or debris before the air passes through the unit. If you have or can find a user's manual, check there for instructions. Or it may be obvious once you start looking. In the USA they are often large square filters that come in standard sizes and slide into the unit, but on a smaller model like a window unit it may be a non-standard size. I do not know anything about HVAC equipment in China.