Homeowners might be in danger if they smell a strong odor of rotten eggs when their air conditioner turns on.
In most homes, the central air-conditioning system shares the duct work and the fan with the furnace. If there is an odor near the furnace, it will be pulled in by the fan and delivered to the vents in each room when the fan is operating.
Two things that have a rotten egg odor come to mind. One is sewer gas and the other is natural gas. Natural gas contains an additive that gives it a distinct odor to get the attention of homeowners in case there is a gas leak. If you suspect a gas leak, leave the home immediately and call the untility company.
Do not turn on lights, use a telephone or start a car that is in an attached garage. natural gas is easily ignited by an open flame or by a small spark.