Last night for the first

Last night for the first time the machine is emitting a gaseous smelling odor. At first we thought it was coming from the house, electrical or outside. Not finding anything which would generate this odor, we turned off the machine and within 1/2 hour the odor was almost gone. The odor caused us to feel nautious, sleepless and my husband complained of a headache. What is this and what can we do. Does it have anything to do with the hepa filter?