About a week ago, we got an email from Jim in Portland, Oregon. He purchased a Speck 2.0 and has been using it to explore how his appliances affect the air quality in his home.
Jim states below...
"The [Speck] reading went from 200 to 7,000 counts while we were running the clothes dryer today! Yikes. Clothes dryer probably pulling in outside air by a vacuum when running according to my engineer son, who knows about particle sensing as he works for Intel Corp."
According to FineHomeBuilding, electric dryers typically act as an exhaust fan and can create lower air pressure inside the house than outside. This pressure change can case a backdraft - by definition, a backdraft can overpower the chimney draft of a naturally vented combustion device - including a furnace, boiler, water heater, or wood-burning fireplace. A backdraft will pull the exhaust particles back into your home (which could be why Jim saw an increase in his Speck count)!
In order to fix the problem, it's best to consult a professional. Reuben Saltzman writes a Home Inspector blog and poses some viable solutions here: http://www.startribune.com/why-water-heaters-backdraft-how-to-fix/226278041/.