The "Haps" are:
1) chemicals that cause serious health and environmental effects. Health effects include cancer, birth defects, nervous system problems and death due ...
2) 188 air pollutants known to have harmful health effects as identified in the Clean Air Act. Most of the HAPs are organic compounds, such as benzene and chloroform; some are toxic metals and their compounds, such as arsenic and mercury.
3) Any air pollutant listed as such in Title III of the 1990 Clean Air Act Amendments. These are chemicals that have the potential to cause serious health effects. HAPs are released by mobile sources and industrial sources. Also referred to as air toxics. Also see "Clean Air Act."
4) hazardous air pollutants
5) A High Altitude Platform Station or HAPS is an unmanned aerial vehicle (UAV) which is to remain relatively stationary at high altitude.