ACH RECOMMENDATION FOR ALLERGY & ASTHMA SUFFERERS
We recommend a minimum of four air changes per hour for allergy sufferers. That being said, we publish coverage rates for 6, 4, and 2 ACH to give YOU the choice in selecting what is best for your specific application. We also do this because amongst air purifier manufacturers, there is little consensus. Some publish rates based on 6 ACH while other 2 ACH, and other still, like Blueair air purifiers, on 5 ACH. Why is four ACH our baseline? You don't have to simply take our word for it!
A minimum ACH rating of four is also recommended by ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) for patient rooms in hospitals. ASHRAE recommends a minimum ACH of six for intensive care units and a minimum ACH of 25 for operating rooms. Again, this just illustrates that as the severity of the condition or necessity of cleanliness rises, so too should the ACH.
HOW TO RECOGNIZE MARKETING PLOYS
So what does all of this have to do with marketing ploys? Many retailers list the recommended room size based on an ACH of two, which can leave some people buying a unit that is too small to handle the size of space they intend to clean. Other retailers list the recommended room size based on an ACH of six, and consumers can end up paying more money for a larger machine when a smaller air purifier would have suited their needs. To cut through this confusion we provide the coverage ratings for two, four, and six air exchanges per hour. So regardless of what different manufacturers may say or how they vary in rating their products, you can do a simple apples to apples comparison amongst nearly all models we offer.
Until there is overwhelming consensus amongst all parties, this problem is likely to persist. Even if manufacturers were to all agree on a standard ACH on which to base their coverage, this measurement is still just an educated guess, at best. Like dehumidifiers and humidifiers, air purifiers operate in a three dimensional world where volume or air is a far more accurate measure than square feet. Square feet is easier to calculate. It's what most consumer are familiar with, but it's also part of the reason why there is such confusion over ACH and coverage, and it's also something that can tweaked or cajoled to put the best face on a product.
http://www.achooallergy.com/learnin...our-recognizing-air-purifier-marketing-ploys/