Alliant Energy wants to warn area residents of the dangers of a gas leak and what they can do to prevent them. Alliant spokeswoman Nancy Craig says fall is a peak time to discover leaks because many residents are closing their windows and turning on their furnaces. She says their company adds a chemical smell to their natural gas to make leaks easier to detect. She says if a leak is detected, residents are advised to leave the home immediately and not to touch anything that could create a spark like a light switch, telephone, or cell phone.