RTI of fire damper and window latches

Does anyone have any info on what the RTI would be for a thermal latch or solder link for a fire damper or fire rated door or window release would be? I have a variety of sources for tests of the RTI of sprinkler bulbs and sprinklers (which are quite high for flush concealed heads) but nothing on solder link latches. I suspect it would be pretty high.

We will put aside the assumption of a flat, unobstructed infinite ceiling in the RTI calculation and application vs a confined window or duct for the meantime…


Flush/concealed sprinklers do not have an RTI Geoff.

A sprinkler RTI is tested by plunging a sprinkler into a heated airstream (in an RTI test tunnel) and measuring the time for activation. Hence, as a concealed sprinkler, with the added complexity of the ceiling itself cannot be plunged into a tunnel.

Concealed sprinklers are listed as “Quick Response” based on a comparative fire test with a standard quick response sprinkler, located (from memory) some 12" below a ceiling. Hence, they are somewhat slower than an exposed ceiling mounted QR sprinkler. It is for this reason that two of the main approval/listing agencies, (FM Approvals and LPC) will not list any concealed sprinkler as QR - only UL does.

In other words - be careful.



Geoff, gobetechnologies.com have a range of fusible links we used for Ansul Restaurant systems so are stocked in NZ by Tyco/Wormald. Never had an RTI for the ML and K range but you could email Globe Technologies for info.


I got a reply from Globe, whcih wasn’t a lot of use.

Hi Geoff,

Sorry about the delay in response.
We don’t have any response time index information.
The load is fluctuating on our links so this make response time hard to establish.

Our ML Link has 10 - 40# load parameters. The response will be much different at 10# load than it will at 40#.
Let me know if you have any further questions.
Best Regards,
Pete Dwan

BRE did some testing on concealed space sprinklers and RTI

From part 5

AP Standard pendent, glass bulb 27.8
BR Recessed (at maximum recess distance), glass bulb 42.4
EC Concealed, domed concealer plate, glass bulb 71.9
CC Concealed, domed concealer plate, glass bulb 104.1
FC Concealed, flat plate, drop down deflector, fusible link, no vent holes 114.9
GC Concealed, flat plate, drop down deflector, fusible link 130.1
DC Concealed, flat plate, drop down deflector, fusible link 284.3

It is also interesting to see what effects poor installation will have to our assumptions on performance

Frame arms ‘normal’, minimum recess distance, favourable concealer plate/lug position and a nominal pressure difference between tunnel and plenum box of 1.3 Pa (considered most favourable conditions possible)
Result used as ‘baseline’ Special
Deviation of sprinkler set-up from Test 1

2 Frame arms rotated 90 degrees, maximum recess distance, unfavourable concealer plate retainer/lug position and a
nominal pressure difference between tunnel and plenum box of 1.3 Pa (considered least favourable conditions possible)
99.7% increase

3 As Test 1, but with 10 ml of water placed in the concealer plate 256.1

4 As Test 2, but with the vent holes in the sprinkler cup housing blocked and no positive pressure differential between the tunnel and the plenum box 414.6 Off scale

5 As Test 1, but with the concealer plate retainer lugs superglued 6 87.8

6 As Test 1, but with the concealer plate retainer lugs glued with araldite 246.3

Thanks Geoff

I had not seen this report previously. At the risk of being pedantic, it doesn’t measure RTI but compares sensitivity.

The key issues include that it states that concealed plate heads do not have the same sensitivity as pendent quick response sprinklers (no surprises here,) but will be effective to maintain tenable conditions under certain fire scenarios. (Again, no surprise here.)

At this stage, I have only read the executive summary, but will read the full report some time on a plane.