It helps, but not a lot. The Pitta mask captured an astounding 0% of 0.3-micron particles and only 64% of larger 2.5-micron particles. In fact, even a surgical mask would provide more protection from PM2.5 than the Pitta mask! Meanwhile, the 3M masks captured over 90%.
Click here to read more on the original test: https://smartairfilters.com/en/blog/are-japanese-pitta-masks-effective-for-use-in-china/