It is no secret that the winter smog in Santiago is bad. The fine particulate (PM2.5) levels are typically above the WHO guidelines for annual (10 μg m-3) and 24-hour (25 μg m-3) exposure. The occasional rain storms clear out the pollution, but it rebounds surprisingly quickly. Exercising with these high pollution levels generally leaves me with a sore throat and feeling lousy. During the winter of 2016 I did not exercise nearly as much as I should, because I did not feel like being out in the pollution while inhaling deeply. So this winter I resolved to buy a pollution mask to wear while outside exercising.
I purchased a RZ mask from an importer in Santiago. The mask included two filters and I purchased a package with an additional three filters. Each filter lasts around for 30–40 hours (depending on the level of pollution).
Since purchase, I have used the mask for six outdoor runs in Santiago. It goes without saying that running is more pleasant without the mask than with the mask, so if I can run right after a rainstorm and before the pollution levels rebound, I prefer that. But, since purchasing it, I have never considered running without the mask when the pollution is bad. The mask seems to seal reasonably well around my face, even with a beard. Though I have no way of precisely determining how much better it does in preventing pollution from entering my lungs, my throat does not feel sore after going for runs, as it did before getting the mask.
The mask has essentially two side-effects:
Somewhat more difficult breathing in, as you have to pull air through the filter. You also cannot breathe through your nose as it is pinched shut by the mask seal. Breathing out is not really affected as there is a 1-way silicone valve that opens up for exhaling but seals shut when inhaling.
The mask traps heat and condensation around your face.
Regarding the first point, I did some informal comparison for running with and without a mask. When not wearing the mask I can usually plod along with my heart rate in the range 130–135 beats per minute while breathing through my nose. As noted, the mask pinches the nose shut, so it is generally not possible to nose breathe (at least not without sacrificing the seal). So when wearing the mask I am breathing through my mouth. In practice I think this translates to a slightly slower pace, to keep my heart rate at the same level. But I probably need more runs and a more careful comparison to say for sure.
On the second point, by twenty or thirty minutes into the run, some condensation is occasionally dripping out of the 1-way valve when I exhale. Condensation builds on the inside of the mask/filter, so I make sure to store it somewhat opened up, to let that condensation evaporate. Given the low humidity here, it generally dries quickly. The inside of the mask is warmer too, but this has not bothered me much, since it is winter, so the extra warmth is usually welcome. On the one or two warm days (>15 C) I have used the mask, it was not an annoyance.
All in all, I highly recommend the mask for running in the heavy pollution here. While I do not have any actual measurements, my throat seems to be faring better when I run with the mask, compared to without it. I would suggest not buying the black mask though, as it looks a bit sinister.