"Respiratory irritants" refers to substances or things in the air that can bother or irritate your lungs and breathing system, causing discomfort or breathing difficulties. Full definition
Coal mining and power production release toxic heavy metals like mercury, respiratory irritants like sulfur dioxide and particulates, and large volumes of heat - trapping gases like carbon dioxide and methane. (blog.harvardlawreview.org)
Other respiratory irritants include cigarette smoke, dust, mold (including in bedding, hay), perfumes, bleach, and cleaning solutions. (houserabbitga.com)
Ozone, the primary component of smog, is a powerful respiratory irritant that initiates wheezing in asthmatics, particularly children. (scientificamerican.com)