I am 63 yrs old and in the past 8 +/- years I have been dealing with asthma. I have a nebulizer,  and 3 inhalers. They work well but I wanted to know what the cause was. I am a retired Residential Real Estate Broker. I am not a scientist but I have spent years happy doing my own research regarding my rashes or my sneezing or my stomach issues that were actually all related to food.  The asthma was different. My doctors and I talked about possible causes. I would track those things, such as barometer pressure change (I have a niece who is sensitive to this), but that was not lining up. I started really digging it different research by very qualified institutions.  The PM2.5 was mentioned several times. The studies discuss air purifiers that filter out this contaminate.  I did some research and looked at the ones the Asthma Association recommended and then of course when to AMAZON. I read the information on the different air purifiers offered and there affect on PM2.5. I ended up buying an Air Purifier that works on just over 1000 sq. My house is 1500 so it does most of it. When you first get it you are supposed to run it one the highest fan speed for 15 t0 20 minutes.  Well, what a difference that made! My den and kitchen/breakfast room areas. My coughing and congestion in null. I now take it to bed since it is in the back of the house and I don't believe it gets the benefits that the other parts of the house enjoy. I am looking forward to when it it is time to order a filter so I can get the one that is made for cleaning the air of everything plus PM2.5. The one I am using now is the first level one and it is doing a very good job. The frugal side of my does not see the need to change but I am very curious what the difference could be. I have noticed such a difference. I just ran to the grocery store to get my Curb Side Order and came home coughing and congested.  It is clearing up now that I am sitting in a part of the house the air filter is cleaning. I am sold on the fact that PM2.5 is the catalyst to my asthma. If you have any questions. Feel free to contact me.