Answer: 99.8 percent.
Called the R-PUR, this mask was designed with the urban commuter in mind. It was made to fit under any helmet, and should appeal to two-wheel commuters who don’t have the luxury of an enclosed cabin to protect against the pollutants in the air.
The trick to the mask’s effectiveness is in its filtering system. It boasts a five-tier filtering system that supposedly catches just about everything, from fine particles to harmful microparticles. There is also an accompanying app that keeps track of the filters and notifies the user when they need replacing.
The R-PUR has been well-received in Europe — it had a successful crowdfunding campaign and earned an official high-performance dust mask certification. It was shown recently at CES 2018 in Las Vegas, and is currently available for pre-order.