For one not so glorious year I played football in Jr High, and despite being one of the smaller guys on the team my position assignment was tight-end. That meant practicing with the linesmen. One drill we would do is two of us would lay on our backs ear-to-ear; when the whistle blew you stood up, turned, and hit the other guy.
Just my luck one day I was pitted in the drill against the largest kid on the team - easily 50 pounds heavier. My only chance at surviving this was to go low and hit his legs, unfortunately he also thought to go low. The whistle blew, I turned, and we collided full force helmet to helmet. I’m not sure how long I was out but the look on the coach’s face when I woke was one of nervous relief.
Today we know more about concussions, and I’m certain the instruction to go “take a rest” in the locker room would be different. As we learn more about hazards to our health the more responsive we can become as a society to help limit the risks of exposure. This goes with air filtration too.
Particle reduction has been the purpose of air filters since they were first used in HVAC systems. However, now we know so much about the molecular pollutants – like VOCs, Nitrogen Dioxide (NO2) and Ground-level Ozone (O3) that cause detrimental health effects. Ozone has been shown to be very harmful to lung tissue and is a cause for COPD, while NO2 is a key component in the generation of Ozone as well as being harmful to lung tissue on its own.
Current standards for air filtration focus only on removal of particulate. Most of the buildings that we work with have only used filters that remove particulate but do nothing to address these harmful molecular pollutants. But as we get more knowledgeable about our environments, especially in urban and city centers, the monitoring of these pollutants is growing. The American Lung Association has a great tool available to access some of these monitoring stations. The EPA is also lowering acceptable exposure limits to these pollutants through its National Ambient Air Quality Standards. (NAAQS)
What this means for building owners and managers is that they will need to learn how to reduce molecular pollutants within their facility. Like anything there are a lot of options available for “Carbon,” Charcoal,” and “Molecular” filtration – the bad news is that most of these filters and smaller air cleaners do a horrible job and are a waste of money. This is due to difficulty in testing, so if a filter manufacturer makes a filter that is black or gray in color it is assumed to be removing the molecular pollutants.
This is coupled with no clear real-world imitating test method, most manufacturers rely on a test developed for WWI gas masks – hardly the conditions your HVAC systems operates on.
The biggest single problem with molecular filtration is this: we try to plug & play molecular filters in systems designed for particulate filters. This leads to molecular filters “failing” and earning the reputation that they don’t work. “Normal” particulate removing filters work by intercepting particles in various ways (straining, diffusion, etc.) and are designed to operate effectively at high air speed – usually 500 feet per minute. However, to remove molecular pollutants the filters must have sufficient residence time – which means slower air speed is important.
The longer the residence time (the amount of time air spends in the filter media) the more molecular pollutants will be removed, here’s a comparison of residence time for different “carbon filters” at the same air speed:
Molecular filtration done properly can yield a much healthier, safer environment for the building occupants. If done improperly or without thought of the specific HVAC system and application spending money on molecular filtration is wasteful and provides no benefit.
Please visit our Molecular Filtration Webpage to review what options you have.