Tell me about HEPA filters

To make a long story short, I unfortunately have my father’s respiratory system, which comes with asthma and allergies standard. I just saw an allergist for the first time in 20+ years, and among other things, she is recommending a freestanding HEPA filtration unit in the bedroom and in the living room to filter the air generally. But when I poked around online to get ideas about what kind, comparison factors, etc., I see that HEPA filters also exist for furnaces, and that there are the regular kind that you would sub for a normal furnace filter, and there are ones that can be built into the furnace system, but that sounds like a PITA. But it might be worth it if it’s feasible, works better, and/or would require less maintenance.

I am trying to figure out how to evaluate the various options, and well, we should get someone in to clean the furnace ducts one of these days anyway, so maybe we can ask what a furnace HEPA filter would involve. (Our unit has a separate furnace.)

Any tips? Evaluation criteria? Things to watch out for? Ways to evaluate potential furnace repair people? (Our upstairs neighbor had a guy in a few months ago, and he looked at our furnace and said the filter wasn’t filtering properly anyway, but I don’t know anything about the guy and only let him take a look because he was offering to do so for free.)

if you have your father’s respiratory system, then he is likely short of breath and wants it back.

lots of allergens might also be on/in your carpets and fabrics. for some vacuum cleaners you can get HEPA bags for it.

the furnace units will plug up and need to be cleaned frequently. dust in your house and heating system will keep collecting.

No answers, but a couple of questions. Is there a respiratory therapist or durable medical goods supplier that you could talk to? Will your insurance cover one, but not the other? Sometimes insurance companies can answer these kind of questions. In fact the allergist who recommended a filter might know.

I’m guessing that the two room system is cheaper. The filters have to be changed when they’re filled and filtering the whole house would run you through filters faster than only filtering two rooms. Also, the furnace blower would have to run all the time to keep the air filtered, which takes more energy than a couple of portables.

In the furnace a HEPA filter will result in significantly lower airflow due to the higher pressure drop across the filter. You will probably need to adjust the fan speed or increase the size of the fan motor to ensure adequate airflow across the heat exchanger.It’s probably not a big deal to do but you can’t just install the filter and assume it’s good.

There are a few things to consider, even if you get a unit installed in the furnace, as mentioned above, you will have to run the “fan” setting at all times. That’s wear and tear on something much more expensive to replace than a portable room unit. You will likely need to replace the HEPA filter in the furnace much more often than you do now with a regular one. HEPA filters are harder on your fan unit to run, as it’s pulling air through a far finer mesh and more layers than a regular filter.

I would do a cost analysis between long term permanent running of the furnace fan and replacing filters, vs. running a couple of room units and the number of filters you’ll replace yearly. Plus the startup cost and replacement costs of a furnace unit/fan motor vs. room units.

Thanks - our bagless vacuum already has a HEPA filter, so we’re covered there. And it’s a condo, not a house, so not as much square footage to deal with (and no damp basement to worry about mold, which is one of my allergens. Possibly the worst one.)

::heavy sigh :: Apparently I picked the wrong year to switch to the high-deductible insurance plan. So the next $1600 or so in medical expenses is going to be out of my pocket anyway, even if my insurance company considers air filtration of whatever sort to be a medical expense.

The asthma isn’t generally bad at all - I normally go months without needing any treatment at all as long as I take allergy meds. I somehow managed to have the worst flare-up in years within a month of switching insurance plans, though. I am still boggled at how treating a relatively mild asthma flare-up and diagnosing the allergy triggers has so far cost going on $1,000 with insurance discounts (would have been double that without). We’re not even talking nebulizer treatment, let alone an ER visit or hospital admission. But that’s probably a subject for Pit thread.

I second the comments about a HEPA filter possibly reducing air flow because it is harder to push air through. Although, as far as the motor is concerned, this actually makes it easier for most fan motors. Notice how your vacuum cleaner speeds up if you block the hose? Like your car spinning its wheels on ice because it can’t get hold of the pavement? It works like that, at least for most kinds of fans. Getting less air to push on reduces the motor load.

I also recommend you consider a room air cleaner, one with a real (and sizable) HEPA filter. I have several made by AllerAir ( I also spent years in the filtration industry and know a lot about such machinery, and theirs are made pretty nicely and do things right. Disclaimer: I have no connection with or interest in AllerAir other than having bought some of their products, and never have.

I think filters of various kinds can greatly improve indoor air quality and respiratory health.

I am considering all options, and the bedroom is fairly straightforward because the door closes. But my main concern is the living room, which is all one open area with the kitchen, dining area, and hallways…I have yet to see a room air purifier big enough to cover that space. I also prefer to minimize the amount of disposable components, because they aren’t cheap, either.

The total space in our unit is about 1500 square feet, so I’m wondering if even factoring in possibly more frequent furnace maintenance, it might not be cheaper and more efficient to go that route? I’m just trying to figure out how to do the math, which might require talking to a furnace guy anyway. Which we should probably do, regardless.