A patio heater is an appliance for generating radiant heat

Thermal radiation

Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....

 for outdoor use.

A burner on top of a post, burns LPG or propane

Propane

Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

, and directs the flames against a perforated metal screen. Heat is radiated from the surface of the screen in a circular pattern around the appliance. A reflector atop the burner reflects heat that would be otherwise lost upwards. The chimenea

Chimenea

A chimenea is a freestanding front-loading fireplace or oven with a bulbous body and usually a vertical smoke vent or chimney.-History:Originally, all clay open fire garden heaters imported to the U.S. from Mexico were known as chimeneas...

 is an alternative to the patio heater for home use, which burns wood instead of gas.

Some newer types of patio heaters are electrically-powered radiative heaters that emit infrared energy onto nearby surfaces, which in turn heat up the surrounding air. Depending on the location, it can be more environmentally friendly (such as North America) or more Carbon Intensive (such as UK )

Patio heaters have become popular with bars and restaurants since they extend the day and the season for their customers to sit outdoors. This increase in the popularity of the patio heater has led to concerns over their environmental effects.