If you have ever been in a climbing or boulder gym, you may have seen that a lot of climbers use chalk powder (magnesium carbonate) to reduce the moisture on their hands and thereby increase their grip on the climbing holds. However, not all of it stays on the climbers hands… part of the powder is suspended in the air, partly due to brushing of the climbing holds when they are covered in too much chalk.
Its use is so popular that during busy hours, you can see the dust flying around in the air. But this is not the problem: the problem is the potentially high level of very small particles, particulate matter, that is invisible to the naked eye. Magnesium carbonate is in itself not considered a toxic substance, but the inhalation of particulate matter is not healthy. Particles smaller than approximately 5 micrometer can penetrate deep into the lungs and cause respiratory system irritation, cough, and pulmonary problems. The risk is higher for people with heart or lung diseases. Besides chalk powder, another source of particulate matter is the rubber of climbing shoes. Friction of the shoes on the climbing holds and walls generates abrasion powder. There is (ongoing) research that suggests that the additives in the rubber may be toxic.
So, it is important to keep the concentration of particulate matter as low as possible. The obvious measures of entirely banning chalk powder and climbing shoes are not feasible, as there is no real alternative. For example, liquid chalk does not create dust clouds but often leaves a residue on climbing holds that is not so easy to remove.
Considering this, Flux Engineering has started a project in collaboration with Grip Boulderhal Nijmegen to investigate the best ways to reduce the concentration of particulate matter. Grip Boulderhal has already been quite active in this area, since the floors are cleaned daily and devices have been installed that ionize the air and use electrostatic forces to capture particulate matter. However, the opening of a new bouldering area (the West Wing) was a motive to investigate the effect of ventilation in more detail.
Although there are regulations and guide lines for the volume of air to be exchanged per hour, this does not guarantee that particulate matter is removed from the gym in the most effective way! Besides the volumetric flow rate, there are other important aspects to consider. For example:
- the geometry of the gym, with its boulders, doors that can be open or closed, etc.
- the way fresh air is distributed into the gym: location, flow velocity and direction
- the way air with particulate matter can leave the gym: passive, or active using ventilators
Flux Engineering has performed measurements of the existing ventilation capacity. Furthermore, we have performed multiple detailed CFD simulations of the new bouldering area using OpenFOAM 12, analyzing different ventilation strategies and their impact on particulate matter movement. The movie below shows one of the considered configurations for the distribution of fresh air. Besides the simulation of air flow, we have performed lagrangian particle tracking simulations to investigate the effect of ventilation on the removal of particulate matter for several different particle sizes, ranging from 1 micrometer to 10 micrometer.
Our investigation has led to some interesting insights into the most effective flow patterns for the reduction of particulate matter, which has enabled Grip Boulderhal to select an appropriate ventilation system.
This is an ongoing investigation, as soon as the new system has been installed we will perform detailed measurements of the concentration of particulate matter to determine the performance of the ventilation in reality. Furthermore, we have adapted the OpenFOAM flow solver to include the effect of ionization and electrostatic precipitation. Stay tuned for updates in the near future!