Exhaust gas gas is undesirable, noxious, or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (properly indicated as CH, but typically shown simply as "HC" on emissions-test slips) from unburnt fuel, nitrogen oxides (NO) from excessive combustion temperatures, and particulate matter (mostly soot). Exhaust gas temperature (EGT) is important to the functioning of the catalytic converter of an internal combustion engine. It may be measured by an exhaust gas temperature gauge. EGT is also a measure of engine health in gas-turbine engines (see below). During the first two minutes after starting the engine of a car that has not
Natural gas vehicle that are not in frequent use. If misused, gas fumes are likely to build up in the car, which can lead to the inhalation of unsafe fumes and possible explosions in the car engine. Other challenges include: relatively price and environmentally insensitive but convenience seeking private individuals; good profits and taxes extractable from small batch sales of value-added, branded petrol and diesel fuels via established trade channels and oil refiners; resistance and safety concerns to increasing gas inventories in urban areas; dual-use of utility distribution networks originally built for home gas supply and allocation of network expansion costs; reluctance, effort