I looked at a Notifier system installed recently by a major local fire alarm company today and found that they have installed Ion detectors in all of the classrooms of a school. I would have spec'd these as photo detectors. We had our first cold night last night and they had 3 smoke detectors in various class rooms go into alarm when the heat came on and burned the dust off the heat exchangers. We only use heat here about two or three months a year (Houston Texas) so dust accumulates in the heat exchangers. Am I wrong on the choice of smoke detectors?
Not necessarily. You have to look at each project from the perspective of what kind of fire you can expect to occur. "Fast flaming" or "slow burning/smoldering". In the first instance "ion" detectors are ideal, in the second, photo-electrics are recommended. Buildings with wooden structures, gyprock, lino floors, and carpet with vinyl-based underlay would benefit from photo-electric type smokes. You have to examine the potential "fuel" and make an informed decision as to what type of smoke detector fits. Of course, "modern" construction techniques always call for the "low bid". In many instances ion smokes are used because they're the cheapest and satisfy the code requirements for "automatic detection devices". They may not be appropriate for the building though, and it's at this point that the designer/engineer has to step in and actually SPECIFY the type of detector to use.
I agree with what has been said. I attended a "Firelight Academy" last week and the instructor (Bob) emphasized that Ion detectors were frequently mis-used because they were cheaper. In this church/school environment I feel that the choice was made on price.
"Allan Waghalter" wrote in message news:_B38h.16948$ email@example.com...
What's even more interesting Allan, is that when I do inspections on buildings, I frequently come across the exact same thing. Recommending that the customer upgrade to photo-electrics is the only option open. Unfortunately the cost involved is sometimes prohibitive. What amazes me is that the units are passed during the Verification. When you read through the standards we use (CAN/ULC-S524 for instance), the requirement for using the correct detector is clear. How this passes the Verification is sometimes beyond me. The same thing goes for stand-by battery requirements. I can't tell you how many systems I've been in to where the customer has added devices (like sprinkler tampers on a retrofitted back-flow preventer) where I've had to "red flag" the panel. What's more, it's been tagged "deficiency free" by a number of ASTTBC registered fire prevention technicians who obviously don't know enough to perform a battery calculation simply based on the amp-meter readings. I've also had an opportunity to work with some ASTTBC techs and have been told by the majority that this aspect wasn't even covered in their training! And don't get me started on the number of non-compliant smokes I've seen installed (where they're not cross-listed to the FACP). Sort of makes you want to tear your hair out. How does one tell the manager of a Strata that their system won't pass muster after it's been "inspected" annually for years (and they have the paperwork to prove it)?
In this case, I monitor this particular system... which is only two years old. The installing company does the inspections. I talked to the owner when I first noticed the presence of the ion detector and he indicated that this is their standard install! They are outside the Houston City Limits, but in the County. The County fire Marshall is very sharp here and must have approved the installation. I can't tell you publicly what they told the school to do over the weekend to prevent the detectors from activating from the furnace clearing out the dust from the long summer.
I am curious as to what requirements are in your Canadian standard for the use of ionization vs. photoelectric detectors. US standards really do not address this issue, probably for fear of pissing off one detector manufacturer or another. In my opinion, it is beyond the skill level of the average fire alarm system designer to determine which type of smoke detector will provide the optimal response to a fire in a particular building, with its specific contents. A fire protection engineer might be able to hazard an opinion on that, but the average fire alarm designer has neither the training nor the expertise to make those calls.
Everyone knows the conventional wisdom is that ionization detectors detect flaming fires faster and photoelectrics detect smoldering fires faster. My point is that I don't really know what kind of fire is likely to occur in a particular building. I don't have that kind of training.
For me, it's a much simpler analysis. Ionization detectors cause lots more false alarms than photoelectrics. If prompt detection of a flaming fire is a design spec, put in some rate of rise detectors. They do a great job of detecting flaming fires, since they produce lots of heat. They also cover a larger area than ionization smokes, and their false alarm rate is nearly zero.
Ionization smokes weren't invented because they were better. They were the original smoke detectors, and we've been stuck with them ever since. Especially since the smoke alarm manufacturers discovered they could make them cheaper than photoelectrics.
In Canada, all fire alarm systems are engineered. That means an engineer signs off on the design and type of detectors he specifies. In some municipalities (such as Vancouver), an additional "test" is required be be met and that is called the Vancouver Building Bylaw. It's essentially based on the BCBC (British Columbia Building Code), but it expands (details) some additional requirements.
To give you some idea of what I mentioned earlier (and hopefully clarify what I said), I'll detail some sections in CAN/ULC-S524-01 (Installation Standard for Fire Alarm Systems). This is a CANADIAN standard to which all the Provincial Building Codes refer. Keep in mind that, while this standard is meant to be the definitive installation rule, it may still be subject to interpretation by the local AHJ or even be modified by Building Code or Bylaw. In all the examples I'm going to cite, I won't be providing the "local modifiers" (at least for the time being):
"126.96.36.199 Fire detectors in areas of high humidty, condensation, steam or corrosion, shall be of a type compatible for such applications."
This rules out ion detectors in areas immediately adjacent to where they could be subjected to steam or high moisture content (pools, spas, showers) however the Appendix to S524 also has this to say:
"A1 General A1.1 Requirements of fire detectors can cover general application rules only, and special circumstances not covered by this Standard may arise. Such circumstances require careful study of the manufacturer's design guidelines, in accordance with good engineering practices and shall meet the requirement of operating the device as intended."
"A3.3 The application of smoke detectors canot be regulated by an installaltion standard for the various types, environmental infuences, such as thermal barriers, air movements and velocity variations, temperature, atmostpheric pressure, relative humity, etc."
While this appears to let the people that write the standard "off the hook", it places the correct use of the type of detector squarely back onto the shoulders of the designer when it also states:
"A3.4 Manufacturer's recommendations should be carefully reviewed and used in conjunction with these requirements.
A.3.5 In order for a smoke detector to respond, the smoke must travel from the point of origin to the smoke detector.
A3.6 In evaluating any particular building or location, likely fire locations should first be determined."
This section determines what kind of detector should be used as well as where they should be located. You are quite correct when you stated that an "installer" (in this case a qualifed electrician) can not determine the best detector for use in a given situation. The Engineer/Designer will provide that guidance based on his experience and knowledge of the code. The AHJ will also review this and the Verification Agency employed by the contractor should be making the appropriate recommendation based on all of the above referenced standards. We have many "checks and balances" in effect here, but not everything is "rosy". For instance, a lot of "Verifying Agencies" are "trained" employees of the manufacturers (or their designated reps) and their "training" leaves a lot to be desired (as I've already noted in this thread).
Most installers don't. That's the realm of the engineer and the individual performing the verification.
All of which are excellent points. The "ideal" (perfect world scenario) would remove the "interpretation" aspect from the codes and standards. This would ensure the kinds of things I've seen happen, don't. Unfortunately neither of us lives in "a perfect world" and we're forced to make the best of it (hopefully with the help of a sympathic AHJ).