Cui X, Li Z, Teng Y, et al. - Given that deposition of fine particles (particulate matter 2.5 μm [PM_2.5]) can happen in the small airways that have an important role in asthma, so, researchers performed this double-blind, crossover study to investigate the pathophysiological alterations in the small airways in relation to using a PM_2.5-removing device in the bedrooms of children with asthma. In a random order, a true filtration device and a sham filtration device was used by the participants in their bedrooms for 2 weeks each with a 2-week washout interval. This inquiry was carried out in a suburb of Shanghai, China, during a low-ozone season. A significant link of true filtration, vs sham filtration, with improved airway mechanics, indicated in a 24.4% decrease in total airway resistance, a 43.5% decrease in small airway resistance, a 22.2% decrease in resonant frequency, and a 73.1% rise in airway reactance, was observed. Significant improvements in fractional exhaled nitric oxide and peak expiratory flow were also observed in relation to true filtration. Findings are suggestive of the ability of indoor PM_2.5 filtration to serve as a practical means to better air flow in an asthmatic lung via enhanced airway mechanics and function as well as decreased inflammation.