Posted By GavinR Hi, Just looking for a bit of advice if possible. We have recently had a series of false alarms on our fire alarm system caused by smoke detectors in use in dusty environments, e.g. steel abrasive blasting and graphite grinding and break out areas. We have considered switching to heat detectors in these areas to reduce the likilhood of false alarms. We have engineered the processes to reduce as much as possible the exposure of the surrounding environment but some tasks can simply not be totally enclosed and as a result we have dusty environment. My question is i have read that heat detectors respond a lot slower than smoke detectors and mostly when the a fire is already well in progress- is this true? Also for dust fire which i believe are extremely rapid would this be suitable? I am contacting insurers and we have requested additonal advice from installation company but would like to conduct my own research as well. Cheers for any advice.

Posted By jervis If you type in fire detection in difficult environments there is a few sites to browse through.

Posted By Mark Eastbourne Hello Smoke detectors are better for early signs of fire so I can understand why you would want them in place. They vary from Ionisation smoke detectors and Optial/Light Scatter detectors. The ionisation detectors work as the smoke smehow effects the radiation and the light scatter detector does as it sounds, i.e. the smoke particles or in your case the dust particles interupt a light beam causing the alarm to be given off. A voting system could be used which would involve two or more detectors linked to the control system but location of each would be an issue and may not work...sorry, just thinking out loud. Regards the heat detectors, there re fusible detectors which which have a solder fuse which melts at a set temperature which may work although would be slow, or a bi-metallic strip which bends on heat creating a circuit. In fact, thinking it through, I would go for the bi-metallic strip positioned near the ignition sources of the area but they are slower than smoke detectors... Sorry mate, not sure if I have helped, just wittered on. Mark

Posted By GavinR Thanks all for your feedback. We have pre-alarms on our systems set to monitor certain levels of particals that will activate pre-alarm or if high enough go straight to full alarm. This is a daily job involving 8 hour shifts of break out operations and additional spells of blasting,etc. My main concern is the nature of a dust fire. From all my research (thankfully not experience) i have been told a dust fire is extremely quick acting and difficult to extinguish. In alot of causes only via emergency services. Now i just don't want to switch from smoke detection to heat should this delay our ability to identify the situation asap. Cheers for advice so far guys.

Posted By Messy Shaw Have a look here at a link which describes Video Smoke Detection. This system uses a video camera which passes it's images through clever software which is programmed to ignore dust/fumes and alert on smoke. I saw one installed in a huge waste transfer hall where dustcats tip their loads to be reloaded on to trains. Very dusty with exhaust fumes, but this system seemed to do the job with few unwanted signals http://www.dtec-fire.com/vsdpage.htm

Posted By Adam Worth Quote - "My main concern is the nature of a dust fire." That worries me! Stop and get that sorted. If you have a fundamentally oxidisable substance then the danger exists for a dust EXPLOSION! not just fire! The physics are that dust settles on hot equipment, gets hot and ignites leading to a primary explosion - this sends other dust up into the air which ignites in a secondary much more devastating explosion! (Someone more knowlagable may care to elaborate on this) That said if your material is not oxidisable it won't happen. Take the advice above and carry out a full DSEAR assessment! Do the chemistry calcs and put your mind at rest! On the note of alarms my current site can be dusty (non oxidisable I may add :) ) and we have occasional difficulties with false alarms. We use a permit system as stated above but also use the false alarms to drive containment improvement - No dust is a much healthier situation to be in!