The smell originates from sulphur dioxide gas which develops from sulphur contained within detergents used during wash cycles as well as other components used by manufacturers such as preservatives etc. . This gas eventually gets released while washing clothes into your home through exhaust vents present on top of washers. It can also get released into your home when using dryer vents since they are not sealed properly. This gas can accumulate indoors causing health hazards if inhaled.