The severe fires throughout California over the past three months have exposed humans and animals to unhealthy air containing wildfire smoke and particulates. These particulates can build up in the respiratory system, causing a number of health problems including burning eyes, runny noses and illnesses such as bronchitis. They can also aggravate heart and lung diseases such as congestive heart failure, chronic obstructive pulmonary disease, emphysema and asthma. Because little information is available to horse owners and even equine veterinarians on the effects on horses of breathing air laden with particulates, UC Davis equine specialists are offering these suggestions to serve as a general guide.