These O-ring sprinklers are being replaced with sprinklers that utilize a "Belleville Seal Design".

More details about the program are available on the company's website.
In July 2001, Central Sprinkler Company announced a voluntary program to replace 35 million Fire Sprinkler heads that use an "O-Ring Seal Design" to seal the sprinkler head waterway.

The Brochure IDENTIFICATION BROCHURE FOR "Central" RESIDENTIAL WET SPRINKLERS in PDF form provides all of the information you need to determine if you have the "O-Ring Seal Design" sprinklers installed in your home. It's each homeowner's responsibility to have them checked and replaced.

Fire Sprinklers Replacement Program
UPDATE - The Fire Sprinkler Replacement Program expired as of August 31, 2007.