Gas lighting explains why a large number of older gas lamps have been converted to electricity. Solar-rechargeable battery-powered gas light controllers can be easily retrofitted into existing gas lamps to keep the lights off during daylight hours and cut energy consumption and green-house gas carbon emissions by 50%. The use of natural gas (methane) for "indoor" lighting is nearly extinct. Besides producing a lot of heat, the combustion of methane tends to release significant amounts of carbon monoxide, a colorless and odorless gas which is more readily absorbed by the blood than oxygen, and can be deadly. Historically, the use of lamps
Small engine dimensions and power output, relative to larger automobile engines. Power output ranges from less than 1 to about 15 horsepower. The smallest of all are used in handheld garden machinery, such as string trimmers and chainsaws, which may be as small as piston displacement. The most common are four-stroke air-cooled single-cylinder engines running on either petrol or diesel. Engines for small machinery that must be hand-carried, such as string trimmers and chainsaws, are usually a two-stroke design, which is lighter for any given power output. However, two-stroke engines create a relatively large amount of air pollution and noise pollution, and