Carbon monoxide (CO) is a tasteless, odorless, and colorless gas. It is a public health concern because elevated concentrations affect human and animal health by reducing the supply of oxygen to body tissues. The primary anthropogenic sources of CO in the Tahoe Region are on-road motor vehicles, residential wood burning, motorized watercraft, and off-highway vehicles. Wildfires are a natural source of CO. Policy and management actions implemented through the Regional Plan to control CO emissions focus on reducing private automobile use through improvements to public transportation and bike/pedestrian trail infrastructure. Vehicle emission standards enacted by state and federal governments also reduce CO emissions in the Region, mainly by requiring improvements in engine and exhaust technologies. The conversion to electric vehicles and the use of non-carbon-based fuels is also expected to have a growing effect on the reduction of carbon monoxide.