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.
|Image from http://drywiredintl.com/lumactiv|
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 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.
Why I chose this machine:
-The PCO component has true UV and titanium dioxide
-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
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 - around 5 air exchanges per hour.
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.
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.
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 go with lots of carbon.
This requires $100 a year in replacement parts.
I will review a few other brands that I ruled out for myself: Air Oasis and HiTech, as well as Airocide.
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 but that seems to be a key component in its air cleaning abilities.
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). There is more of a discussion of this brand and their technology in the comments as this machine claims to be doing something different than just a PCO or just an ozone machine.
HiTech Air Solutions
|The inside of the 110 model $5995|
(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
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 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.
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.)
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 prevalent 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).
Since writing I have heard one bad reaction to Molekule with about 50% of the people 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. For high VOCs I would focus on filter that has a lot of carbon. My interest here is in a house with extremely low VOC levels and already extremely low levels of mould. And the hope here is to keep the air as mould free as possible.
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.
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 is not sponsored by Vornado. The Amazon links are Amazon Associate links. The Molekule discount link does provide me the ability to earn points towards buying one and I would really like to try this machine.
This post was written with the technical assistance of an engineer, though the opinions and conclusions are my own.
This post was written in June 2017, was updated in Spring 2018. I do my best to keep all my posts updated if there is new information.