Updated 2020

PCO Air Purifiers – Which Ones Reduce Mold and Which Ones are a Scam.

PCO (photocatalytic oxidation) is a technology that breaks down mold, VOCs as well as some pathogens.

My interest in these air purifiers comes from first-hand accounts of this helping people with mold and VOCs and from the studies showing the eradication of mold and mycotoxins.

This is a technology that is extremely promising for those sensitive to mold and it’s important that we test this out as much as we can. I’m really urging the mold sensitive community to gather more data on this by trying some of these machines.

I am really excited about this technology as something that can safely break down mycotoxins and odors. Some people may be interested in its effects on breaking down viruses and bacteria as well.

What is PCO?

In photocatalytic oxidation, UV light hits a catalyst, usually titanium dioxide, creating hydroxyl radicals (OH). These OH molecules bind with and break apart pollutants into harmless molecules.

My recommendation is based on the most affordable and effective products that I have found. Upon purchase, I earn a small commission through affiliate links at no extra cost to you.

The Best PCO Air Purifiers for Mold

What I’m Using – The Best of Inexpensive PCO Air Purifier – Vornado

I use the Vornado air purifier. The Vornado PCO300 and PCO500 are air purifiers with a great value. It is a PCO air purifier, plus it has true HEPA and activated carbon. Most PCO units are much pricier or don’t include all three air purification methods.

True HEPA and activated carbon capture dust, pollen, pet dander, smoke, bacteria, mold spores, dust mites and odors including VOCs.

PCO and carbon are the main technologies used to reduce odors and VOCs. (Ozone can as well, but it is very risky, I have a post all about ozone).

PCO actually breaks down molecules including molds and mycotoxins. I like that it has all three main air purification methods.

Why I chose this machine:

-The PCO component has true UV and titanium dioxide
-Respected brand name
-Noticeably brings down odors in new apartment and new cargo trailer
-Has a 5-year warranty
-Replacement parts are reasonably priced ($25 bulb every year, $35 titanium dioxide screen every 5 years – for the PCO related parts)
-Does not put out ozone

What I don’t like about it is that the unit itself offgasses, though not everyone thinks so. After two weeks I found it to be good.

The difference between the two sizes is that the 500 has a lower low speed and a higher high speed. The 500 has 2x the HEPA and activated carbon of the 300.

They both have the same PCO technology – so if you want to increase the effectiveness of the OH molecules in a large space you would want two of the 300 instead of one 500.

The 500 moves 184 CFM and is advertised for 265 sq ft – which is around 5 air exchanges per hour.

What are Air Exchanges per hour (ACH) – Air exchange per hour is how many times you are “replacing” the air in the room per hour, this is a key area of comparison with air purifiers.

ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) recommends a minimum of 4 ACH for patient rooms in hospitals, 5 for intensive care units and 25 for operating rooms. For the purposes of those extremely sensitive to mold and VOCs, we want about 5-10 air exchanges per hour.

To maximize how much air in the room the air purifier can process, put it in a central location.

How do you Calculate the ACH from a Unit Specs – You always want to find the CFM of the unit. The CFM is the capacity of the unit to move air – how much air it moves through the machine. CFM stands for Cubic Feet Per Minute. You need the CFM to calculate ACH. I made two calculators to calculate ACH from CFM and CFM needed from the room size and desired ACH.

Some other PCO units are more or less the same unit re-branded: Continental Fan CX1000, Catalytic Pure Air, Field Control Trio / Sun Pure SP-20C. They seem to use a very similar PCO catalyst style to the Vornado with a titanium dioxide plated metal screen.

GermGuardian – Something Smaller

Another brand that is very affordable that also incorporates HEPA, carbon, and PCO is GermGaurdian. I have heard of people using it in trailers and being happy with. At $89 it’s a steal. And it has 5.5 ACH in 171 sq ft.

Top Pick for PCO Air Purifier – Molekule

The Molekule –  If I had to go back and pick one right now, I would choose Molekule. Though I still might want another unit with HEPA.

And if I was dealing with off-gassing, I would add in one of these air purifiers with lots of carbon.

Molekule (CFM 80, 1 air exchange per hour in 600 sq ft, $1200) is a slightly different technology called PECO. 

Here is a summary of their studies – very promising results on eradicating mold. The data they showed me showed it worked better on mold than PCO.

This company has well respected big names behind the design. The inventor of Molekule is the person who discovered PCO. He has an impressive resume.

I will be trying this machine out as I think it is very promising.

The company started in 2016 and with the momentum they have had since then, I do think they will be around for a while.

The warranty is only 1 year, which is short compared to the others.

If you can afford it, if design is important to you, and you’re using this in a relatively small space like a bedroom, this is my top pick. 

This requires $100 a year in replacement parts.

The new Molekule Mini which is coming out soon provides 1 air exchange per hour in 250 sq feet.

The average-sized bedroom is around 130 sq ft and could be up to 250 sq ft.

I’m aiming for 5 air exchanges per hour. So the regular-sized Molekule would still be insufficient in a 250 sq ft room in terms of what I need.

Even in a 150 sq ft room, the original Molekule cannot provide 5 air exchanges per hour. I would stick with the regular-sized Molekule for almost any sized room.

Here is my calculator that helps you size an air purifier for your room based on how many times you want to overturn the air in an hour.

Brands I Ruled Out

Air Oasis and HiTech, as well as Airocide.

Review of Air Oasis for Mold Reduction 

The Air Oasis 3000G3 model is rated for 3,000 sq ft and only moves 11 CFM of air. 3,000 sq ft at 11 CFM is 0.02 air exchanges an hour. That is very little air movement.  (I am using 8 ft ceilings in my calculations of CFM to ACH). But that’s not important if you are using this as an ionizer.

Air Oasis does more than just filter air that moves through the machine like other PCO air purifiers it also, as the company states, “creates ionized hydroperoxides” (AKA it’s an ionizer) which puts out ions and ozone. tt is now meeting California levels of safe ozone (CARB).

You can have one made without the ozone production component but that seems to be a key component in its air cleaning abilities. I do not consider any level of ozone unless it is minuscule, to be safe to use in occupied spaces.

It has a 3-year warranty and the replacement parts are $80 every 2 years.

I know this brand because it is being promoted by top doctors. I was surprised when I dug into it to see how ineffective it would be at moving air through it, and that it gives off ozone (it was not approved by CARB at the time of writing the original version of this).

There is more of a discussion of this brand and its technology in the comments, as this machine claims to be doing something different than just a PCO or just an ozone machine.

The newer Idapt Air is similar but claims to produce 0 ppm of ozone. This is something I would be more likely to try.

It contains a HEPA filter, a carbon filter, PCO technology and a bipolar ionzier.

Most ionizers give off ozone but it is possible to produce ions with minuscule ozone. They claim 0 here.

Review of HiTech Air Solutions – Is it a Scam?

HiTech Air Solutions, a brand known among some extreme mold avoiders, makes Air Reactors that claim to be PCO machines. And wow, what I found out was very disturbing to me.

To start, the 101 model ($2000) is very expensive relative to the other PCO machines. From looking at the inside of the machine they use basic components that total under $150 for all visible parts: four foam/coarse dust filters, two UVC lights, two computer fans, and a 4U 19″ rack case.

The claim here is that some of these filters are photocatalysts that produce OH molecules – that there is something invisible called “Technosite®” (no evidence of this trademark with USPTO) impregnated onto the filters.

They may be using something similar to PALCCOAT (confirmed not partnering with this brand) which is a clear titanium dioxide catalyst (FYI $13 per square meter). I have found no evidence of a patent held by HiTech or Ray Robison, owner, on anything in the machine.

I have also seen two other odd claims from sales reps of the company – one, that the filters are coated with Sporax (I have seen pictures of their filters with Sporax, though they later denied this.) And that both the filters and the bulbs are also coated with something proprietary – both things that I would want to know are safe to use with UVC light.

HiTech makes some pretty astonishing claims that not only have not been backed up by evidence but feel free to ask a chemist about how this is even possible:

They claim their OH molecules (which are produced by the PCO process) last much longer in the air than the other air purifiers’ OH molecules (~6 weeks instead of ~15 seconds) based on “a study by Texas Tech”, though this study cannot be produced by the company. Dozens of phone calls were made to track down the existence of this study and nothing turned up. Even more, the University claims it does not conduct studies give the results on the phone and then withhold the report for large sums of money (as the reps claim).

I have not found any evidence that this “study” exist or that this produces a totally different kind of OH molecule. Just ask a chemist how you can have a stable but also reactive OH molecule.

I would like the company to disclose what they are using in this machine so we can know if it is safe and effective, or, provide real studies that show which molecules and byproducts this machine produces.

The burning smell is worrisome to me. I have seen photos of users machines showing the filters having being burned through by the UV light. That will produce offgassing. The accounts I have seen of bad reactions are also worrisome.

HiTech claims it produces 99.9% pure air. I have seen no studies to back up this very broad claim. What is the level of contamination in the air to start, and what is “pure air”? Also note, PCO technology does not filter particulate pollutants (EPA).

I have contacted a technical rep, sales rep and the owner for these studies – they responded but were not able to provide them. Others have contacted them as well for this information.

The HiTech 101 is 142 CFM and claims it can be used in 1600 sq ft which is only 0.7 air exchanges per hour. Their bigger units are ~$5000 and ~$6000 dollars!

The HiTech sales reps make 25% commission off each unit and they usually recommend multiple units for houses. The commission for the three sizes is roughly: $500, $1000 and $1500! The cost of the replacement parts are $140, $190 and $295 per year, for the three different sized units.

HiTech has not submitted their Air Reactors to CARB at the time of writing, to confirm they give off a safe level of ozone. However, the bulbs they are using are USHIO brand UV bulbs with a 2G11 / PL-L base which do not give off ozone. They use another brand as well, LSE Lighting UV bulbs, with the same base. From what I can tell this bulb would not be any different from the USHIO brand.

I’m calling on HiTech reps, especially doctors to consider the following:

• We don’t know what is in the machine – it is invisible, not disclosed, and the company has not backed up the claims of which molecules and byproducts this machine produces
• The company has made numerous unsubstantiated statements – there is no evidence of any university studies, no evidence of FDA approval, no evidence of a patent, no evidence of a trademark (on Technosite)
• I have seen people have bad reactions – it is not proven to be safe
• This machine is an unnecessary financial burden on patients in my opinion when there are well-established brands selling verifiable PCO machines on the market for a fraction of the cost
• Making $1000+ off each (medium-sized) unit is certainly a nice incentive for sales reps, though ethical concerns must take priority

FDA Approval of PCO Machines

The FDA approvals I have found are one for a PCO machine involving titanium dioxide (it proved to destroy some bacteria, viruses and mold) for specific commercial uses.

The Airocide and Odorox also have FDA approval as type 2 medical devices for use in hospitals. These all use titanium dioxide and UV; The FDA approval cannot be stretched to make safety or health claims on any device that deviates from this technology or has unknown additional technologies.

HiTech claims to be FDA approved, I can find no evidence of that. Anyone can search for FDA approvals here.

HiTech did respond to this article, some of the statements have changed from what I have records of, and the updates are in the comments. They have since put out some “study result photos” with no evidence of a study.

Review of Airocide Air Purifier 

Another popular PCO machine that has been around for a while is Airocide (CFM 14 “Cleans any size room” which I suppose is technically true, but is not going to get you 5-10 air exchanges in most rooms).

This doesn’t move a lot of air, but I like that the website has studies confirming that it doesn’t give off ozone, and a short study on breaking down mycotoxins.

It looks cool which is a major plus.

The claims about removing dust, dust mites and allergens are not all that accurate since PCO machines do not filter particulate pollutants (EPA).

It has a 5-year warranty and 60-day money-back guarantee which I like. The main drawback here is how little air it moves.

100 a year in replacement parts.

Most of the PCO machines do not include HEPA and activated carbon like the Vornado, they are more expensive, they don’t move as much air, and their replacement parts are more expensive. (Airocide has a unit that contains a charcoal and MERV filter for $900.)

Adverse Reactions to PCO Hydroxyl Generators

I have heard of people having bad reactions to HiTech. I have heard only one bad reaction to Airocide, and a couple of bad reactions to AirOasis.

I do not know what accounts for these bad reactions. It does not appear that there is an ozone issue (apart from AirOasis). Dr Daniel Cagua Koo has also noted that some patients simply don’t do well around this technology.

Since writing I have heard of some bad reactions to Molekule with about 50% of sensitive folks buying it being happy with it, and the other half not, and one bad reaction to Germ Guardian.

It is possible that PCO is creating harmful byproducts in high VOC buildings.

If you are in high VOCs I would focus on a filter that has a lot of carbon – like these I review here.

My interest here is for a house with extremely low VOC levels and already extremely low levels of mold. And the hope here is to keep the air as low mold as possible.

HiTech reps speculate to buyers that the bad reactions may be helpful (some kind of detox or herx), which is ethically unsound in my opinion. With no data to suggest this is detox, we should take a precautionary approach.

I would love to hear from more people who have tried these other brands. Let me know if you have had good results or a bad reaction to a PCO machine.

Do PCO Machines Give off a Burning Smell

According to Airocide, the UV bulbs themselves emit a bit of a burning smell at first. They burn theirs in for two days, but sensitive people can smell it for up to a week.

The Vornado PCO had a very slight burnt smell at first which seemed like the smell of carbon.

HiTech states that the burning smell is mold/mycotoxins breaking down. I see no evidence for this claim.

Airocide made a statement that mold does not produce a smell when broken down by OH molecules.

A HiTech user also stated that the UV lights have burnt right through the “reactor pads”. This is consistent with a theory that the UVC lights are burning the “reactor pads” and causing a smell.

Corinne Segura is a Building Biologist with 6 years of experience helping others create healthy homes.

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This post was written with the technical assistance of an electrical engineer, though the opinions and conclusions are my own.