Sweet Odor from Carbon Filter

A Reader writes:

I am an allergic-asthmatic, my wife has chemical sensitivities, and my son has allergies.

We were considering buying an IQAir HealthPro Plus, largely on the strength of your review and recommendations.

So, we found a local retailer who had one on display for people to look over.

We were impressed with the overall quietness on speed settings 1-4, it looked to be well built, and it didn't come off as quite so big as we thought it would be from pictures and measurements.

However, we noted a sweet odor, somewhat like fresh paint, coming from the outlet of the unit, at all speeds. The shop owner wasn't aware of it, but then he had an ozone generator blasting away in the corner, the whole time we were there.

I called IQAir about the odor and asked them if the sweet odor was to be expected. I forgot to mention the ozone generator running in the background.

I was told that it was more likely that something in the store had saturated the charcoal filter and that we should expect such odors as the charcoal filter became saturated.

Just to be sure, I called back the next day and asked if the ozone generator could have caused the charcoal filter to become saturated. I was told that the ozone would have reacted with the plastic of the housing and filter cartridges and could cause outgassing from that interaction.

While I had the woman on-line, I also asked her about reports of slight outgassing from the V5 cartridge during initial use. She didn't acknowledge that, but she did say that the glues and binders in the pre-filter and the HEPA filter would outgas for some period (unspecified) when new, and that the set-up instructions had you run the unit on high with the windows open for so many hours for just this reason. Doug Sylvane confirmed this information about the set-up, but couldn't confirm the reason for it.

Have you experienced the outgassing from any or all of the filter cartridges in the HealthPro Plus?

If so, do the odors actually dissipate or are they just diluted by having the air purifier running all the time, and do you as an individual with MCS find them at all irritating?

The last thing, after I told Doug Sylvane what I've just told you, he suggested any of the AllerAir 5000 series as a better choice for us, this based on AllerAir being the only manufacturer to construct their machines to avoid the unit introducing any outgassing byproducts into the air themselves.

They do this by building the machines without plastic parts, without glues and binders, with inert rubber seals, and cotton pre-filters. In your experience and/ or based on your own research, would you agree with Mr. Sylvane's suggestion?

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Ed's Reply

Hey Reader;

The ozone will have reacted with everything in the store, creating partial oxidation byproducts, yikes!

It is also common for charcoal filters to get a sweet smell after a period of use. Molecules are held to the large internal surfaces by adsorption (not absorption).

So, unlike a quality HEPA filter's ability to retain %99+ of all particulate until resistance climbs, carbon filters continually release gas molecules, albeit at a slower rate than they are accumulated.

As the carbon accumulates load, its efficiency declines.

How do we know if a gas phase pollutant is in our breathing space? We don't really know to change the carbon until we smell an "odor."

Many toxic chemicals are dangerous below the olfactory threshold.

This is a principal driver of my enthusiasm for sensor driven automatic air purifiers like the new BlueAir E-series, see reviews Blueair 650e, 550e.

Some carbon cartridges have a break in odor when new.

Sweet smelling gas filters are a very common issue, I get numerous inquiries.

I have had three new IQAir V5 carbon cells with no issues. But readers report the sweet odor in both new and slightly used carbon cells.

My Sharp Plasmacluster washable carbon bag did get a sweet smell after a year or so, but it mostly washes out. I do not know what causes this, but suspect the very ubiquitous aldehydes (formaldehyde/acetaldehyde).

The AllerAirs are very good choices for the chemically sensitive, but any carbon filter will require frequent changes unless your home is clean of gas phase pollutants.

Good Luck,

Ed