An engineer with asthma asked me about the particle sizes from the different inhalers. This post is for him. This photo illustrates the different particle sizes of the currently available inhaled corticosteroids. (Source: Martin RJ. Therapeutic significance of distal airways inflammation in asthma. J Allergy Clin Immunol 2002; 109 (2 suppl): S94-S460.) QVAR is beclomethasone dipropionate HFA and has been shown to deposit more medication in the lungs and less in the mouth and throat. However, the clinical significance is not known. There is no proof thus far that smaller size confers superior control of asthma. We know that other characteristics of the molecules play a role in the effectiveness and safety of the molecule.