Inert Gas Clean Agent Extinguishing System Units

The existing requirement to operate all system cylinders within 1-second maximum time interval between the first and last cylinder/valve assembly may be overly restrictive. The 1-second requirement is important for the chemical clean agent fixed extinguishing systems of UL 2166 (and the prior UL 1058) given the short system discharge time of 10 seconds and to ensure multiple cylinders can discharge the two-phase agent into the shared manifold in a timely manner. It appears the requirement was carried forward into the UL 2127 inert gas extinguishing systems standard. With the duration of inert gas system discharges (typically 60 seconds and often up to 120 seconds) and the likelihood of installations incorporating a significantly greater number of cylinders than corresponding chemical clean agent systems, an increase in the permissible actuation time is reasonable. Large installations may necessitate longer actuation system lengths and the present 1-second requirement may be restricting these installations unnecessarily. There is also a typographical reference in Clause 30.2 that needs to be corrected.