I have a APC back-ups XS1300 hooked up to my macpro early 2008. It is in the spare bedroom. I keep the door shut when I am at wook to keep out pet dust and dander( dog and 3 birds). When I go into the room in the evening I notice a smell of ozone. The only thing it could be is the UPS. It is plugged in but switched off. Anyone else have this problem?