Your ceiling diffuser is quite easy to remove and clean.
Installed before 2000
For these older units, the diffuser twists off counter clockwise when looking up at the diffuser.
Installed between 2000 – 2007
To remove the diffuser, simply pry down one edge of the white trim ring using something flat such as a butter knife. Continue to work your way around the ring until you have a 1/4" (7mm) or so gap all the way around. Then simply grab onto the edges and pull straight down. The diffuser lens can be cleaned with soap and water. To reinstall the diffuser, position the 4 zip style ties into the 4 holes on the ceiling ring and push up until the diffuser is flush with the ceiling.
Installed between 2007 – September, 2010
Simply pull the diffuser down.
Installed after September, 2010
You'll need to twist off the diffuser counter-clockwise.