Re: Efficiency for Dust Mites and Pollen

A Reader writes:

Hi again Ed Dear Ed,

First, congratulations on your website.

It is easily the most useful and informative site on the internet about air purifiers.

One thing that would be useful to include in your reviews is the system efficiency for removing particulates in the air.

Most manufacturers state the filter efficiency but keep quiet about the whole system efficiency (except IQAir). I was about to purchase a Blue Air purifier when I stumbled upon this video on Youtube: Blueair dust-up.

Basically it demonstrates that even Blue Air machines have a lot of bypassing and are not sealed properly. I wonder how it could be rated as 98% efficient by air-purifiers-america.com... Now I don't know anymore what to think.

Some brands look good on paper like RabbitAir and Sharp, but their true efficiency is unknown. I understand that buying a laser particle counter is probably prohibitive, but it would be the true test to apply.

What do you think?

I need an air purifier to remove house dust mites and pollen during the spring season. I know that another leaky purifier won't help as I had a big Honeywell in the past (the biggest one they make) and it didn't do any good. What would you recommend (for a bedroom about 130 sq. ft.)?

I was thinking of the Alen 350, which seems well sealed but I don't know about long term reliability, as it is made in China. I can't afford the IQAir.

Best Regards,

A Reader.

Ed's Reply

Hey Reader;

While it is true that the Blueairs are inefficient due to the weak sealing around the top filter, killdirt.com's video is a setup.

The Blueair system is an electrostatic filter, which depends on tight seals much less than a big true-HEPA like IQAir.

First, what kind of shop has 2,600,000 .3 micron-and-up particles in the air?

He had to do a mega dust-up to get readings that high. See my IQAir review where the most I could raise was 440,000, with the same particle counter.

I think he set the top filter very loose just for the video.

But this does not mean Blueairs are tight, that top filter is held down mostly by gravity. This would be very easy for me to remedy, but seems out of reach of the average consumer.

Air cleaners run the gamut from 10% to 99% efficient, with the majority at an estimated 60%. Even some very good machines, like Sharps, Rabbits, and Austin Airs struggle to stay in the 70's.

The only published efficiencies are on Air-Purifiers-America's site, which is a front for the Alens, owned by the Alen founder, a former Dell Computer executive here in Texas.

Their ratings, while useful on a relative basis, are obviously biased in favor of the house brand. (Alens are good air purifiers, but not on a par with IQAir as Air-Purifiers-America tries to imply.)

So the truth is we do not know the true efficiency of any air cleaner other than the zero-blowing IQAir, and probably cannot.

This is especially the case when considering efficiency on a long term basis and under different loading conditions.

Also remember that efficiency is meaningless without specific particle size. The $2k laser counter in the video measures particles bigger than .3 microns, prices rise quickly for sensitivity to finer stuff.

Again, see my IQAir Healthmate Plus review, where I play with a borrowed IQAir particle counter just like the one in the video.

I'm not so sure that better efficiency is the sole answer for your situation. Marginally less efficient air cleaners, like the Blueairs, will just take longer to achieve similar results, though none will match the low particulate levels achieved by IQAir in the end.

Dust mite droppings are not primarily an airborne allergen in the usual sense. They arise when we toss and turn at night and agitate the pillow and bedding. Air purifiers can do little to interdict a source so close to our noses.

Pollen should be easier to interdict. Figure out where it is coming inside and seal it out. Once pollen gets indoors, it is hard to get rid of because its just the right size to fall to the floor quickly, then stir up when doors open or feet create currents.

Shoes could be left outside during pollen season, it tracks in like snow. At my cabin, my washer and dryer are outside on the porch. When I am good and dirty I shed an outer layer of clothes outside.

I have been testing furnace filters modified to fit in my windows, kind of like a window unit air conditioner. While not allergic to pollen, I have winter wood smoke at the cabin and traffic soot in Houston.

I get a MERV-7 or better 12 by 36 furnace filter and cut it down to 35-something to fit the window, open the window, insert the filter and push the window edge down to hold it, and seal edges with 2-inch transparent tape.

In Houston, I am now using a 3-inch thick built up window filter with 1/8 inch carbon and multiple furnace filters in series. This is attached to a dual-fan thermostatically controlled window fan - the kind with expansion panels similar to window-unit AC. This has improved the incoming air considerably, and ought to keep pollen out.

The quickest way to increase efficiency is to seal the edges of the HEPA with scotch tape, being careful not to overload the motor.

Some machines will burn up short term, like my Hunter Permalife, but I have several experiments running now that are holding up.

Any of the Asian air cleaners, Sharps, Rabbits, even the Winixes, can be sealed with tape.

Some of these, notably the Sharps, have bypass ducts. There is an air-purifier-power frequent contributor with a complete seal experiment on a Sharp FP-P40Cx running now. I don't do or recommend sealing a slip-designed air cleaner this tightly, but this power user will report results in a few more months.

Sincerely,

Ed