Both Underwriters Laboratories and Factory Mutual have provided opinions that while the new marking system must be applied to all sprinklers manufactured after the effective date, it will not apply to listed sprinklers manufactured prior to the effective date.  These sprinklers can be maintained in inventory and sold and installed at a later date without any violation of their listing.

A letter written to NFSA Vice President of Engineering Russ Fleming dated December 7, 2000 from Mr., Kerry Bell, Associate Managing Engineer, Conformity Assessment Services of Underwriters Laboratories, contains the following statement:

"As indicated in UL's standards for sprinklers, the new SIN (Sprinkler Identification Number) markings become effective in January 2001.  Up until the effective date, the manufacturers are permitted to mark production sprinklers using the "old" model designations.  Therefore, it is anticipated that a substantial amount of sprinkler inventory in manufacturing and distribution facilities, which does not have the SIN marking, will still be available for sale and installation after the effective date.  UL Listed products manufactured without the SIN marking prior to the effective date are still considered Listed even though they may be purchased and installed after this date."

A letter written to NFSA Vice President of Engineering Russ Fleming dated December 8, 2000 from Mr., Richard Ferron, Hydraulics Section Engineering Specialist for Factory Mutual Research, contains the following statement:

"Factory Mutual Research Approved sprinklers manufactured prior to January 1, 2001 may utilize their original marking designations or may utilize markings in compliance with the NFPA 13 requirements assuming the manufacturer has submitted such changes to Factory Mutual Research.  Either marking designation is acceptable to Factory Mutual Research and not does violate the terms of the Approval.

"Historically, sprinklers manufactured and inventoried at the end of a calendar year have been sold and installed during the course of the following year.  The only way to prevent this from happening would be to mandate that the manufacturers destroy their complete inventory of sprinklers at the end of each year.  Not only is this detrimental to the manufacturers but Factory Mutual Research believes that the additional cost associated with the destruction of perfectly good sprinklers would be passed along to the end users.  This increased cost could mean the difference of a property being sprinklered or not."