Please be aware that prolong idling of cars has become an issue for some units especially with the increase in electronic start ignitions. 

Prolong idling pollutes the environment, wastes gas, and can emit small amounts of carbon dioxide that can enter a unit.  It can also damage an engine including the catalytic converter.

Check out the FAQ sheet on idling cars:

http://www.hcdoes.org/airquality/Anti-Idling/IdleFAQ.htm

Thank you for your attention in this important matter.

Experts say that idling a car engine more than 30 seconds is unneeded even in the cold weather.