I'm An Indoor Air Quality Inspector. I Tested The 4 Ways To Clean The Air In Your Home.

I set our furnace fan to run all night for a month.

The first fix I tested was the one I used to recommend most. I already had a good MERV 13 filter sitting down in our furnace slot. It cost about $24, and the packaging says it lasts up to 90 days.

The trouble with central filters is simple: they only do anything when the furnace blower is actively blowing air. In most houses, the heating or cooling system runs less than 25% of the time, even during heating and cooling season. The rest of the time, that filter just sits there in the basement dark while the air upstairs stays completely still.

If you look up how to clean bedroom air with a furnace, every forum tells you to switch the thermostat fan setting from AUTO over to ON. That forces the central blower to run 24 hours a day, non-stop. So that is exactly what I did for 30 straight days.

My counter at the pillow started at 14 at bedtime. At 3 AM, after the blower had been pushing air through the house for hours, the counter sat at 12.

It barely made a dent. Like most bedrooms, ours doesn't have its own return vent. When we pull the bedroom door shut at night, the supply vent blows air into the room, but very little of that air can squeeze under the bedroom door and travel all the way back down to the furnace filter in the basement.

Running that heavy blower motor all night also came with real headaches. You could hear air rushing through the metal duct right over our bed all night long, which Laura pointed out the very first evening. Our electric bill that month came back about $35 higher than normal just from spinning that blower.

You can't just fix this by jamming a thicker, denser filter into your furnace rack, either. When a filter is too dense, it cuts the system's airflow. I've been in plenty of homes where a heavy filter froze up the air conditioning coil, and the family ended up going back down to a cheap MERV 8 just to keep the system running.

When I pulled our MERV 13 filter out after 30 days, it had plenty of grey grime in the pleats, but that was junk gathered from the whole house, the basement, and the hallway. Our upstairs bedroom was the very last place that air ever reached.

Score: 3.0/5. Keep a good filter in your furnace to protect your HVAC system, but don't count on it to clear the air over your bed.

The little plug-in unit put a dark shadow right above our outlet.

The second product I tested was the little plug-in style purifier. These are the devices my clients ask me about the most because they're small, completely silent, plug straight into the wall outlet right next to your nightstand, and don't require you to buy replacement filters.

I bought 2 of them online for about $40 each, and plugged one into the outlet right beside Laura's nightstand.

The first thing people worry about with these units online is ozone, and they have good reason to worry. A lot of small plug-in devices are actually ionizers. Some ionizers produce ozone as a byproduct, which is why California caps the amount of ozone an indoor air cleaner can release at 0.050 parts per million. Breathing in ozone can damage your lungs, and the people who reach out to me about it most are folks with asthma, pet birds, or cats.

Even if you set the ozone question aside, the numbers on my counter told the real story. At bedtime, the counter at our pillow read 13. At 3 AM, it read 12. That is pretty much the exact same reading we get when nothing is plugged into the wall at all. Because these units don't use a physical filter, there was nothing to pull out at the end of the month to see what had been trapped.

Then came day 18.

I bent down to check the plug and noticed a faint grey shadow staining the white wall paint right above the outlet. I've walked past that exact shadow in dozens of clients' bedrooms over the years. I took a tape sample off our wall and put it under my microscope. It was packed with regular household dust, shed skin flakes, and stray clothing fibers.

That is how an ionizer actually works. It doesn't trap anything or take it out of the bedroom. It just shoots an electrical charge into the floating dust so the dust sticks to the nearest surface, whether that's your drywall, your headboard, or your carpet. The dirt never leaves the room. Every time you walk past the wall or pull the sheets back to make the bed, you knock that exact same dirt right back up into your breathing space.

I pulled both units out of the wall that morning. I've walked past them in clients' bedrooms for a decade, but from that day forward, these little plug-ins are the first thing I tell homeowners to throw in the trash.

Score: 2.4/5.

Our HEPA machine only really cleaned the room when it was too loud to sleep.

Next up was a standalone HEPA machine. I picked up a popular, well-reviewed brand sized properly for our bedroom square footage, which cost about $230. I set it up in the corner across from our bed.

Here's what most people don't know when they buy one: that room rating they print in big letters is calculated with the fan running full blast on its highest setting. The second you turn the machine down, it pulls significantly less air through the filter. When you put it on the quiet night setting, it barely pulls any air through the paper at all.

My counter showed the gap right away. When I kicked the machine all the way up to its highest fan setting, the reading at the pillow dropped from 13 down to 4 in about 45 minutes. It definitely catches dust when it moves air.

When we switched it over to sleep mode, the bedtime reading was 13, and by 3 AM the counter was still sitting at 11.

To actually clean the room, that machine has to run all the way up all night long. At full blast it's about 53 decibels, a steady roar a few feet from your head, and almost nobody can sleep through that all night. Noise is the number one complaint I hear from homeowners, and my own house was no different.

Laura lasted exactly 2 hours that first night before reaching over and switching it down to the quiet night setting, and that is where it stayed for the rest of the 30 days. That is what happens in almost every home I inspect. People buy these machines with good intentions, find out they can't sleep with it on full, turn them down to the setting that does almost nothing, and eventually pull the plug.

Our unit was completely off on 3 separate mornings during the month. The display panel glowed bright enough to throw blue light across our ceiling, it let out a loud beep every time you touched a button, and the exhaust blew a cold draft right across Laura's side of the mattress.

By the end of the month, the intake filter was visibly grey and covered in fuzz, but the surface of Laura's nightstand right next to it still had a layer of dust on it every 3 or 4 days. Replacement filters for that unit run between $60 and $70 every 6 to 12 months, which adds up fast.

Score: 3.4/5. It's a solid filter, but only if you can sleep with it running full blast, and most people can't.

That's when I stumbled on Barnakl.

Near the end of that month, I was doing an inspection for Mrs. Patel over in Upper Arlington. I carried my small step stool into her master bedroom, climbed up to take my usual tape sample off the top of her ceiling fan, and stopped. There were black pads on top of the blades, each one held in a small white clip.

Mrs. Patel saw me looking, laughed, and told me they were called Barnakl. She explained they were filters made specifically for ceiling fan blades, and said she slides out the old pads and slides in fresh ones every 30 days. She even opened her nightstand drawer and handed me one she had taken out the week before. It was coated in thick, matte grey grime.

I asked if I could take it home with me. That evening, I put Mrs. Patel's used pad under my microscope in the basement. Packed inside the material were carpet fibers, shed skin flakes, clothing lint, dog hair, and several grains of tree pollen.

It's called Barnakl Pearl, and the design is dead simple. A small white clip sticks to the top of a fan blade, and a black pad made of activated coconut-shell carbon slides into it. Every 30 days you slide the old pad out and a fresh one in, and the clip stays where it is. From the floor, you can't see them. Every time the blade goes around, the air goes through the pad instead of past it.

I had my counter in my bag, so before I left I asked if I could take one more reading. I held it by her pillow with the fan running, and it read 5. Then I walked down the hall to her guest room, same house, no pads on that fan, and it read 13. I'd been in a lot of bedrooms that month, and hers was the lowest number I'd seen.

Our ceiling fan already runs over our bed 8 hours a night, and Barnakl has a 30-day money-back guarantee, so I had nothing to lose.

I put the pads on our bedroom fan and checked the counter every night.

Our bedroom fan has 5 blades. I wiped the tops of the blades, stuck the clips on, gave the adhesive 10 minutes to set, and slid the pads in. Laura walked into the room later that evening and didn't even notice they were up there until I pointed them out.

There was nothing to plug into a wall outlet, no fan motor humming in the corner, no glowing lights shining on our ceiling, and no buttons to beep when you adjust them. Our fan ran on its normal medium speed all night, exactly the way we always run it.

The reading on my counter told the story. At bedtime, the counter read 14 at pillow height. By 3 AM, night after night, the counter dropped down to 6.

New After 30 days

On day 30, I climbed back up on the stool and slid the pads out of the clips. They had gone up solid black, and they came down a dull, dusty grey. Under the microscope, I found the exact same carpet fibers and skin flakes that our rug and bedding shed every day, along with outdoor pollen that we must have carried in on our work clothes. The fan had pulled all of that junk directly out of the air right over our bed.

To be fair, there are a few honest downsides, but very few. You have to have a ceiling fan in the room, and you have to leave that fan running for them to work (which we do anyway). You also have to climb up and slide in fresh pads every 30 days.

Even with those drawbacks, this is the only filter that actually cleaned the air over our pillows without waking us up.

Score: 4.8/5.