A high pressure ridge settled over the central Rockies. Aside from the haze and particulates, weather was perfect for hiking in Rocky Mountain National Park. However, hiking can be an aerobic-like activity, and an increasing number of scientific studies have found that haze and particulates injure lungs. Occasionally, Rocky personnel at entrance gates have posted warnings about bad air: children, elderly, and individuals with asthma are to minimize exertion, remain in vehicles if possible. Not surprisingly, much of the haze comes from growth and development along the Front Range and in Estes valley. I'm saddened when I stay indoors running an air filter on days that ought to have been splendid for hiking. I'm saddened to wear high quality face masks in Estes Park on days when particulates and haze are abundant.