Zak Bagans of Ghost Adventures mentioned in Season 4: Episode 16 Return to Goldfield Hotel that he was wearing a dust mask because he had been recovering from a serious respiratory illness and wanted to be safe from asbestos, black mold, dust, and other contaminants the crew encounters when investigating. The illness wasn't explained. It is unclear if he has a chronic respiratory illness.
The episode first aired on January 14, 2011 and was filmed in Goldfield, Nevada as a follow-up to an investigation that took place six years earlier.
The final episode of the seventh season of Ghost Adventures, Death By Wild West is set to air on November 30, 2012. Zak, Nick, and Aaron will recap their investigations of Nevada, California, and Arizona where they encountered ghosts from the Wild West period.
In November 2012 Zak revealed that filming for an eighth season of Ghost Adventures is taking place. No premiere date has been set yet.