different brands of air purifiers have different effects, but it is certain that they can remove particulate matter, but the scope and efficiency of removal are different. The best way to judge is to know the filter screen level (the higher the filter screen level, the higher the filtration efficiency. At present, the HEPA filter screen level used to remove PM2.5 is generally H13) and ask the manufacturer to give the test report of this type of machine (the report must be complete, not just one page); Light a cigarette for testing (you can choose a detector). Generally, after one cigarette, PM2.5 can be off the charts (5), to test how long the purifier can hit a safe value.