Emissions from LPG Engine CO HC NOx vol. CO is a very toxic, colorless and odorless gas. When engines operate in enclosed spaces, such as warehouses, buildings under construction, or tunnels, carbon monoxide can accumulate quickly and reach concentrations which are dangerous for humans. It causes headaches, dizziness, lethargy, and death. CO is usually the major concern whenever LPG engines are used indoors.
Hydrocarbons are also a product of incomplete combustion of fuel.
LPG emissions, because of the composition of fuel, contain only short chain hydrocarbons. They are not likely to contain toxic components which are found in gasoline HC emissions. However, hydrocarbon derivatives are responsible for the characteristic smell which is often a nuisance when LPG engines operate indoors. Nitrogen oxides are generated from nitrogen and oxygen under the high temperature and pressure conditions in the engine cylinder. Nitrogen dioxide is a reactive gas, very toxic for humans.