The Best Air Purifiers for Mould - A Review of PCO Machines

PCO Air Purifiers - Which One I Use and Which Ones are a Scam

PCO (photocatalytic oxidation) is a technology that breaks down mould, VOCs as well as some pathogens. My interest in these air purifiers comes from first-hand accounts of this helping people with mould and VOCs and from the studies showing the eradication of mould and mycotoxins.

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This is a technology that is extremely promising for those sensitive to mould and it's important that we test this out as much as we can. There has been so much talk about HiTech (both good and bad, which claims to be PCO) but very little talk about the more recognised and more affordable brands - I'm really urging the mould community to gather more data on this by trying some of these other models.

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

A very brief explanation of PCO is that UV light hits a catalyst, usually titanium dioxide, creating hydroxyl radicals (OH). These OH molecules bind with and break apart pollutants into harmless molecules.

What I'm Using

I use the Vornado air purifier. The Vornado PCO300 ($260) and PCO500 ($470) are the air purifiers with the best value on the market that I have seen. It is a PCO air purifier plus it has true HEPA and activated carbon. Other similar 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, mould spores, dust mites and odours including VOCs. PCO and carbon are the main technologies used to reduce odours and VOCs. (Ozone can as well, but it is very risky, I have a post all about ozone). PCO actually breaks down molecules including moulds. 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
-Noticeably brings down odours 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

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 - around 5 air exchanges per hour.

I am using it to offgas a cargo trailer but I will test it on a slightly mouldy place and report back. It does offgas but I have never used an air purifier before so I cannot compare. I think it is about the same as the smell of a portable AC. Another less sensitive friend thought it had very little offgassing.

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.

I will review a few other brands that I ruled out for myself: Air Oasis and HiTech, as well as Airocide and Molekule.

Air Oasis

The Air Oasis 3000G3 model ($500) 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.

Note on air exchanges per hour (ACH) - 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 mould and VOCs we want about 5-10 air exchanges per hour. This Air Oasis has 0.02 air exchanges per hour. (I am using 8 ft ceilings in my calculations of CFM to ACH.)

Air Oasis does more than just PCO it also, as the company states, “creates ionized hydro peroxides”  (AKA it's an ionizer) which puts out ozone and does NOT meet the California regulations on a safe level of ozone (CARB). You can have one made without the ozone production component.

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, and that it gives off unsafe levels of ozone (as determined by CARB).

HiTech Air Solutions

The inside of the 110 model $5995
HiTech Air Solutions, a brand known among extreme mould avoiders, makes Air Reactors that claims to be PCO machines. 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 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 claims to be doing something different than the others. 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 produces a totally different kind of 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 the studies that show which molecules and byproducts this machine produces. The burning smell is worrisome to me. 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 interested in this company 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 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 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

The FDA approvals I have found are one for a PCO machine involving titanium dioxide (it proved to destroy some bacteria, viruses and mould) for specific commercial uses. The Airocide also has FDA approval. HiTech claims to be FDA approved, I can find no evidence of that. Anyone can search for FDA approvals here.

Other Popular Brands

Other popular PCO machines are 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, $600.) 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. 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.
Molekule (CFM 80, 1 air exchange per hour in 600 sq ft, $800) is a slightly different technology called PECO. Here is a summary of their studies - very promising results on eradicating mould. It is very beautifully designed. They have only been in business for a year (since 2016) so I would be worried about the possibility that they won't be around to provide replacement parts. The warranty is only 1 year, which is short compared to the others. If you have a lot of money and design is your main concern this one could be considered.

Both of these require $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 used to have a unit that included HEPA for $800, which is not available right now.)

Adverse Reactions

I have heard of people having bad reactions to HiTech. I have heard only one bad reaction to Airocide, and a couple 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). I don't have enough data on all these machines to know if bad reactions are more prevelant with any particular brand.

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 (other than to the plastic or glue of the unit).

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

The 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 mould/mycotoxins breaking down. I see no evidence for this claim. Airocide made a statement that mould 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.


This post is not sponsored by Vornado. The Amazon links are Amazon Associate links. My recommendation is based on the most affordable and effective product that I have found. Buying your products through these links helps support me and this blog.

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

This post was written June 2017. I do my best to keep all my posts updated if there is new information.


  1. Hi Corinne,

    I’m a fan of your writings. I’ve looked into air purification some too. Here are a few thoughts for your Reader’s consideration.

    1. Vornado - I worry that many of the PCO oxidants the machine puts out are going to be drawn back into the unit and neutralized by the carbon. For this reason, I never run my IQ Air purifier with carbon along with my Air Oasis that uses PCO technology just for this reason. Air mixing is vital regardless of what air purifier you're using.

    2. Air Oasis - 11 cfm - Mold remediation expert Greg Weatherman has a video with a 2,000+ cfm blower showing virtually no air movement a couple of feet from the machine! I'm guessing the folks at Air Oasis selected the fan sized based upon a calculated exposure time to the UV lamp - see my article on the UV Light Tube I built. Air exchanges and cfm are irrelevant when it comes to selecting a small PCO device. Of course, there are whole house PCO units and then it’s important to select a unit based upon the cfm of the furnace blower. It's the number, quality, and type of oxidants produced that matter. Having said this, I do question the actual area these units can treat. I guess it depends on the level of contamination.

    3. Ozone is a powerful oxidant. People apparently run ozone generators in enclosed spaces. I've written about how this can lead to undesired by-products in my article on autos and mold. The Air Oasis with the default lamp definitely puts out ozone. If you stick your nose right in front of the output, you'll cough. For this reason along with the importance of air mixing, I always run my Air Oasis with a ceiling fan on along with moving the unit about the house. For your readers that are really chemically sensitive, I believe you can ask for a lamp that doesn’t produce any ozone.

    4. Titanium dioxide is the bare minimum for a good PCO machine. Air Oasis uses a mix of metals they believe work even better as I wrote about in my Air Oasis article. However, anyone can "talk a good game". The key point is that the reason some CIRS doctors are recommending them is because a preliminary study of 48 homes showed they made moldy homes livable again along with findings as in the video. Personally, I fine that there is a big difference in the air quality after running the Air Oasis in the main living area of our house overnight. I love having it because I can clean up the air after having guests that invariably track in toxins.

    Be well,

    Biotoxin Journey

    1. Hi Greg, I was looking for your article on Air Oasis but I could not find it. I would love to read it before responding. -Corinne

    2. The Air Oasis article is in the Members section. You'll need to create a free account and login.

    3. Hi Greg,

      I found the article thanks. My response to above:

      1. The air moves through the Vornado first through the HEPA/carbon and then through the PCO aspect. So the OH molecules are flowing out, away from the HEPA/carbon. They would not move back against the air flow. They also only last a few seconds so all the action is on the catalyst not really about moving them through the air.

      2. If the unit can't move much air through it it just can't be effective - it just won't reach the air in the room. If the air needed more time on the catalyst then you would need many Air Oasis units per room.

      3. The Air Oasis emits ozone because it's also an ionizer. This level if higher than what California Air Resource Board finds is safe for healthy people. Those of us who are sick or sensitive should certainly follow these guidelines. The machines cannot be sold in California. Ozone has a long half life so I would not feel comfortable running it in one room in the day and another at night.

      4. It's difficult to compare Air Oasis to the others because it is an ionizer and creates ozone. This will have some beneficial effects but the long term effects on people's lungs could be serious. Titanium dioxide is the industry standard - it's what NASA uses and the FDA approved machines are using titanium dioxide. So I do not know the effectiveness of using other metals. There would have to be a study comparing different technologies that does not also add ozone or an ionizer to the picture.

    4. Corinne,

      I don’t want to get into this too deeply but here is my understanding.

      1. PCO technology does produce hydroxyl radicals (OH) along with hydro peroxides (HO2) and hydrogen peroxide (H2O2). The peroxides can linger quite a while in the air.

      H2O2 lasts about 24 hours in the air – until it reacts with a toxin.

      2. If we were simply relying on the fans of any of these units to move particles about, the air would never get thoroughly cleaned. In my opinion, the small fans on these units are simply to throw oxides into the air. The quick OH reactions within the units are nice but due to their very short life and limited air movement don’t do much. It’s the peroxides and overall turbulence of the air in the room that matters.

      Capture Zone Limitation of Air Scrubber

      3. The Bi-Polar ionizer is to help get dust particles to stick together so they fall to the ground. The ions can also zap some toxins. I’ve never read of ionizers producing ozone. On the other hand, UV lamps definitely produce ozone and this depends mostly on the type of glass and the special coating (doping) on the inside of the lamp. For example, GPH lamps are standard quartz lamps available in both “ozone-free” (G, GPH lamps) and ozone-generating (G...VH, GPH...VH – VH stands for Very High ozone) versions.

      Quartz Lamp Specs

      4. Regarding studies, there was a preliminary study with 48 homes of folks with CIRS. MCS and CIRS folks are a sensitive group. The Air Oasis cleaned up their inadequately mold remediated homes to the point that they could live in them again. Having said this, titanium dioxide is the standard for PCO technology.

    5. I have not seen info on PCO creating hydro peroxides (HO2) and hydrogen peroxide (H2O2) as part of the air purifying technology

      I spoke to AirOasis - they say their specific PCO catalyst produces hydro peroxides (HO2) and hydrogen peroxide (H2O2) which regular PCO does not produce in any significant amount. (Not sure if they have studies to back that up).

      They said they use ozone producing bulbs which the others don’t do. It sounded like if someone requests a no ozone version they are changing the bulb. They claim the ozone is important in what makes the peroxides.

      They use a Bipolar ionizer, they claim it doesn’t give off ozone but ionizers in general do produce ozone:

      Not all UV lights produce ozone, as you mentioned there are non ozone producing bulbs and that is what Airocide, Vornado, HiTech and others are using. Airocide has a study showing no ozone production, you can see the HiTech bulb used.

      Talking to the companies is not the best way to get accurate information though I wanted to get Air Oasis' response to this. My intention was not to anaylze the technology of the any of these units because this would take very specialised expertise in chemistry or engineering. All I can say conclusively about Air Oasis is that it moves very little and and it produces more ozone than is considered safe in California. I can also conclude that the other units do not produce ozone.

    6. Well, this is turning out to be an interesting conversation.

      I think you’re right about PCO technology that uses titanium dioxide (Tio2). More credible sources say TiO2 produces mostly Hydroxyl Radicals (OH) along with some Superoxide (oxygen with an extra electron). I’d initially thought all PCO technology produced basically the same oxidants. As you’ve noted, hydroxyl radicals and superoxide react really quickly – fraction of a second for OH and maybe one second for superoxide.

      So the production of hydrogen peroxide (H2O2) by Air Oasis appears to be a unique result of the 5 different metals they use (silver, nickel, rhodium, copper, and titanium). As noted, H2O2 lasts many hours and ozone has a half-life of 30 minutes. Maybe it’s the longer life of these two oxidants that makes it possible for the Air Oasis to clean up moldy homes that were inadequately remediated.

      So it turns out that knowing exactly what these machines are producing matters. If you have a Vornado using TiO2 that’s only producing very short lived oxidants, then you need a decent sized fan and good turbulence in the room as the only air that gets cleaned is the air that actually passes through the machine. If you’re using an Air Oasis, then fan size doesn’t matter because the oxidants produced will waft around in the room for some time until they hit upon a particle they can react with. With either machine, getting good air turbulence in the room is essential.

      As you’re stated and I agree, I don’t think it makes good sense to run an Air Oasis in unoccupied rooms. Depending upon the amount of turbulence along with other factors like the amount of furniture and carpeting in the room, the levels of oxidants that build up may very well be harmful. Having said this, I really do think there is way too much concern over ozone. If I’m living in a building that is literally killing me due to high levels of biotoxins, I think running a machine that can knock out these crushing toxins makes good sense even if it does produce a little ozone. Besides, I can always put the machine in an unoccupied room and if I’m really concerned, I can use a timer and have the machine turn off an hour or so before I enter.

      (continued below)

    7. Regarding the Bi-Polar ionizer that is also inside the Air Oasis, I stand corrected regarding ozone production. Apparently whenever there is an electrical discharge, ozone is produced. For examples, hair dryers, copy machines, and electrostatic air cleaners also produce ozone. That being said, WikiPedia says the amount of ozone produced is small and given the size of the Bi-Polar unit, I think it’s a stretch to think that a person needs to be concerned about the amount of ozone that unit produces. If that’s the case, then one should really steer clear of waterfalls too as they produce a fair amount of ozone. It’s always a question of degree and weighing risks versus benefits.

      On the other hand, I have tinkered a bit with UV lamps and I can assure you that depending on the wavelength, glass, and coating, they can produce a lot of ozone. And I mean a lot! As you noted, Air Oasis will fit their machines with a non-ozone lamp if requested. So the meaningful level of ozone coming from the Air Oasis is coming from the lamp.

      As a point of reference, if I run my G3 3000 Air Oasis in the basement with little furniture and concrete floors, I can pick up the faint smell of ozone after several hours. If I run it on the main level with more furniture, I don’t smell any ozone. Does the level of ozone get above the 0.05ppm in federal guidelines, I don’t know. What I do know is that I don’t need to tax my body any more than it already has been so I generally don’t sit in the area of the house where the machine is running.

      Initially, my main points were that getting good air turbulence is way more important than fan size, that the ozone coming from an Air Oasis isn’t due to the ionizer, and that I’d personally chose to use a machine with at least a rudimentary study showing that it actually helps clean the air in real world situations – even if it does produce a little ozone. As you stated, anyone can “talk a good game”; what matters is if the machine actually makes a meaningful difference. Along the way, I’ve learned that not all PCO machines produce the same oxidants and that this matters at least in terms of fan size and that ionizers do produce a nominal amount of ozone.

      Thanks for this discussion Corinne. The effort and care you take in your writings is a testament to your concern for the well being of others and big heart.

  2. Hi Biotoxin Journey - In one of Corrine's comments, she said that the Air Oasis representatives said that if you choose to get an Air Oasis without the ozone, then it wouldn't produce the same peroxides. (And therefore it would probably be less effective)... and in one of your comments, you said that it is the combination of the different metals that is producing the peroxides, not the ozone. Which is true? If I were to get an Air Oasis, I would choose to do it without the ozone. Despite the conversation here that it is not the most harmful thing in the world, I really don't need to tax my body any further. I am trying to decide between trying the Air Oasis and the Vornado. P.S. do you work for Air Oasis? I know there is a warranty regarding parts, etc. But if you try it and it just doesn't work for you, is there a money-back guarantee? Thanks!

    1. Hi Carrie,

      I definitely don’t work for or have any financial ties to Air Oasis. I just think it’s a good machine based upon my research. You can read about my health journey at

      That was an interesting point Corinne brought up about the Air Oasis not producing peroxides without using an ozone generating UV lamp. Apparently, the combination of ozone, UV, and multi-metal catalyst are required to get the full benefit of the machine. In other words, PCO technology in general involves shining UV light on a metal “catalyst” and from what Corinne has learned, we also need ozone for the production of peroxides in the Air Oasis.

      Anyway, I totally understand if some folks just don’t want to expose themselves to any level of ozone. While I’m somewhat sensitive to chemicals, I certainly don’t have anywhere near the reactions some with MCS have. I just thought I could round out this topic with some of the material I’d learned in studying about the Air Oasis. Regardless of what machine you use, I’d definitely run a room fan to help get the Air Oasis peroxides out into the room or move un-cleaned air to the base of the Vornado.

      I got my Air Oasis from and they do have a 30-day return policy.

    2. Thanks for your reply. I wasn't concerned about you having any financial ties to Air Oasis, I was more interested if you know about their guarantee. I will check out the site you mentioned and call them too. Aside from the ozone concerns, I am interested to see if the claims that many people make about Air Oasis could be true for me as it seems that it has helped so many people. I'm particularly interested in the travel model they make now which would be amazing if it helped with visiting other people's moldy homes or being able to work. I may give both the Air Oasis and the Vornado a try since both seem to have a way to try them out and return if they're not helping. Thanks !

    3. One more question and thank you! Your journey is inspiring and I look forward to reading your site more. Without the ozone, the unit would still be putting out hydroxyls to search and destroy right? Just making sure it wouldn't change that feature

    4. Carrie,

      Hydroxyl definitely will not search and destroy. They are highly reactive and will burn up within a fraction of a second. Also, I can’t say for sure what’s produced without ozone in the Air Oasis. I’m assuming from what I know about PCO in general and what Corinne found out that without ozone the bulk of the oxidants are hydroxyls. It’s sort of a moot point though because if you’re not going to use ozone, I’d personally go with the Vorando. Just based upon its size, I’m guessing it produces more hydroxyls than the Air Oasis without ozone. Besides, it’s got HEPA and carbon.

      Regarding the portable Air Oasis unit, I have one for when I travel. Recently, I was down South and unfortunately picked a moldy hotel. I’d had a long day and it was really late to change hotels. I thought I could tough it out. I was wrong. After nodding off for an hour, I woke up with that familiar feeling of high excitability in my body. Ugh.

      I was running the small portable unit but there was no way it was going to keep up with what was pouring out of the A/C. Desperate, I took the sheet of plastic I always bring with me and laid it on the bathroom floor. I normally use this plastic under the mattress cover. On top of the plastic, I laid down a heavy blanket. I closed the door and fired up my portable unit. It was enough. The fight-or-flight reaction calmed down considerably and I was able to get some sleep – albeit a bit rough. These machines definitely have their limitations.

      Well, that’s it for me on this topic. I'm bowing out.

    5. Thank you so much. I appreciate your help and clarifications!

  3. This comment has been removed by the author.

  4. Any suggestions regarding optimal humidity levels for PCO devices? I keep my house around 45-50% to avoid mold growth, but I'm concerned that the PCO devices (Air Oasis, etc) might need 55-60% for optimal performance. Thoughts?