I used a Respro while mountain biking in AZ; when breathing & inhaling very heavily there is some resistance. But otherwise I liked it. There is also this inha

I used a Respro while mountain biking in AZ; when breathing & inhaling very heavily there is some resistance. But otherwise I liked it. There is also this inhaler containing ectoine, but this wouldn't protect against particles entering the brain via olfactory nerve: "An inhaler that protects the lungs against air pollution has been developed by scientists and could help the many millions of people affected by toxic air to avoid its worst effects." https://www.theguardian.com/environment/2016/sep/16/new-inhaler-protects-lungs-against-effects-of-air-pollution https://www.theguardian.com/environment/2016/sep/16/new-inha...