PCO and incomplete breakdown by-products
Okay, I am sure everyone is familiar with these studies:
I have read the criticisms of the first which I believe amount to concerns about the catalyst used. Fair enough, perhaps.
If PCO based technologies can process high VOC concentrations without deleterious byproducts what are the required conditions and are there any scientific references to support the safety of this method?
Basically, I want to see safety data type studies for any of the specific PCO based solutions available.
By way of background, I am looking at a filtration / purification solution involving a Sanuvox UV Lamp preceding a Lennox PureAir ( belt and suspenders approach to reducing microflora and their microtoxins - and yes I need to do this) but I have concerns about byproducts from the PureAir.
Thanks for any comments.
With you being new on the board and all I can't really elaborate much further than this because I am not familiar with who you are. Here is one version of the original paper. Ask your self why they would use and ozone producing UV lamps to activate the catalyst when they had to have know it would skew the test results. There are many other reasons their PCO test failed if you read this paper real closely you might pick up on the real facts. Many papers reference this paper and quote it blindly with out validating the results.
Searching for information on the effectiveness of UV combined with Photocatalytic Oxidation on pollutants from wood smoke I came across what I think is the same document on the DOE site:
Evaluation of a Combined Ultraviolet Photocatalytic Oxidation(UVPCO)/Chemisorbent Air Cleaner for Indoor Air Applications
What I take away from reading through this is UVPCO own it's own may acutally increase net production of formaldehyde and acetaldehyde
For me this puts a hold on making any "snap judgements" on installing this technology in my home. It certainly seems that the homeowner systems that are currently being marketed are long on hype and short on facts. Has the FAA approved any UVPCO systems to date?f
I am just a homeowner whose children have complex medical problems. I know very little about any practical aspects of HVAC. I do have some background in biochemistry and physiology.
Originally Posted by genesis
Thank you for the full text, very helpful, I will try to read through it this evening.
It seems you are suggesting the additional ozone creates more carbonyl groups in the reaction space potentially stabilizing certain cleaved VOCs into aldehydes. This seems reasonable as a thought experiment, but I want to see that verified in properly conducted science.
My need to understand the conditions under which performance data is gathered is underscored in this situation, e.g., what happens on a humid, high ozone day when the HRV is pumping ozone into the return?
I have found two studies with findings of incomplete breakdown and emission of harmful byproducts. I cannot find any studies that show a lack of these byproducts in something approaching a residential application.
If using UVA and different catalyst can ameliorate VOCs without byproducts then I don't understand why a major vendor like Lennox, for instance, cannot publish relevant performance data demonstrating safety.
Assuming there are confounds or flaws in the methodology still does not assuage my concerns. I have potentially flawed science on one hand and no published science on the other.
For what it is worth, I would much rather install a PureAir into my system than try to rework it to accommodate 100+ lbs of carbon. Unfortunately, it seems I have to leap blindly and run a risk of aggravating extant medical conditions if not in fact creating more.
I am not attacking anything or anyone and I have no agenda, I simply want to see compelling science that demonstrates safety of anything which may have impact on the health of my children.
Incidentally, I have been trying to get a response from Lennox on this subject and they have been cagey to say the least.
Thanks for the comments.
But nothing looking at production of formaldehyde and acetaldehyde. It also doesn't attempt to qualify what effect each stage, filter, UV light or photocatalytic had. Not saying it doesn't work. Just doesn't address the issue of VOC formation.
Originally Posted by genesis
Calls UVPCO an emmerging technology and suggest it may be effective with upstream GAC which is something the Berkley paper points to as being important.
Again doesn't address the issue of formaldehyde and acetaldehyde. This is seems to be an application for an award? I come away with the feeling that UVPCO is a promising technology which requires an engineered system and while you've certainly put a lot of work into maximizing the benefits most of the research has been on effectiveness in reducing live contagions from the air stream.
I really come away more than anything with the feeling that most off the shelf stand alone UVPCO devices being marketed now are merely a component and adding willy nilly to a homes HVAC system is at best going to improve air quality very little and quite possibly introduce problems.
Wilt take a look at this paper. Might help you a bit since you have a chemist back ground.
Originally Posted by WillT
From the above referenced paper:
That's not at all what I would expect. I would bet dollars to donuts that increased concentrations of outdoor ozone are a marker of high levels of industrial pollution. Therefore other contributors to BRS would also be higher in these areas; both chemical and pschological (i.e more stressful environment).
In the absence of ozone chemistry, one would expect the indoor concentration of VOCs in the study buildings to vary randomly, without correlation with the indoor or outdoor ozone concentrations.
Pretty damning report for polyester/synthetic filter media in comparision to fiberglass. The study doesn't attempt to isolate any particular cause for BRS. The lower indoor concentration of ozone suggest that it's not the ozone itself but the reaction of ozone with other chemicals that may be to blame. It could be that the poly/syn filters provide a better reaction media for this to occur. In other words, by doing good (higher concentration of pollutants in the filter) the net result is bad.
Last edited by Alden_Sloe; 10-24-2008 at 01:37 PM.