Indoor Air Quality in Climbing Gyms

What follows is an engineering discussion about Indoor Air Quality (IAQ) in climbing gyms. I will use big words and diagrams. You will be bored. Do not keep reading…

Indoor Air Quality (IAQ) is a general term for how “good” indoor air is to breath. There are different measures for IAQ that account for things like the amount of particles in the air, harmful organisms, odor, etc.

In climbing gyms, the main IAQ concern is particles in the air (chalk). I’ve left the gym many nights with red eyes and white snot from all the chalk in my gym. There are 4 main ways to reduce the amount of chalk in the air in climbing gyms.

Source Control
This is likely the cheapest and most effective way of improving climbing gym IAQ. By restricting the use of chalk (i.e. require chalk balls or don’t allow chalk), the source of the problem is reduced or removed. This, however, isn’t ideal because many people prefer using loose chalk. In monopolized areas (“but it’s the only gym!”), I suggest the management ban loose chalk. This is harder to do in more competitive areas (read: Boulder ).

Ventilation
A simple way to clear the air is to blow it out of the building. This works great during good weather because fresh, clean outdoor air doesn’t cost anything, however, this becomes very expensive during cold or hot weather because of the cost to heat or cool.

In arid climates, many gyms use evaporative coolers to cool the air in the summer. This method of cooling costs less, and consequently, the gyms should be able to increase the amount of outdoor air supplied.

Ventilation is measured in Air Changes per Hour (ACH). This is how many times the air in a space is replaced with filtered, tempered air (recirculated and outdoor air mixed); outdoor ACH is how many times the air is replaced with tempered, filtered outdoor air.

I suggest gyms provide at least 2 outdoor ACH, and a total of 4 ACH (or more). Additionally, the gyms should (and are probably required) to have economizers on there air handlers. Economizers are the things that allow 100% cool fresh air to be supplied during mild weather.

Filtration
Filtration is cleaning the partilces out of the air. All air handling systems have some filtration.

For the particle heavy air of climbing gyms, the filters should be staged (i.e. an okay filter then a good filter). This is cheaper than using a single filter because the good filter is protected by the okay filter. I suggest climbing gyms use staged filtering with the secondary filter having a MERV 11 rating (although I still need to research particle size).

Some gyms use separate systems to filter and temper the air, such as this filter system. You’ll notice that those filters are all washable, so waste is minimized. Increasing the filteration means less air changes may be required to maintain the same quality of air.

Air Movement
In critical areas such as operating rooms, the air moves from the ceiling, down onto the patient, then is sucked out of the room at the floor. This is so the air doesn’t pick up organisms, recirculate, and get into the patient. The same principles should be applied to facilities with a lot of particles.

Chalk is stirred up while climbing, and tends to fall to the ground with gravity. In a gym such as The Spot, the chalk is all stirred up near the ground level. It makes since then to pull dirty air to a low air return, instead of pulling it towards the ceiling and through the breathing zone (4-6′ above the floor).

Air flow patterns in climbing gyms.

In a gym such as the Boulder Rock Club, chalk is stirred up through the height of the gym. It would make the most sense to have low and high air returns in this case (although it is often cheaper to only have high returns and that’s what they have).

Indoor Air Quality is relatively easy to control in climbing gyms. With a little planning and investment, the air could be much healthier in these facilities.