There used to be some very knowledgeable people on this site who could answer better than I but, with some experience in sprinkler design & install, I'll weigh in...

First, the stairway sprinklers are only going to activate if that is where the fire is located. In other words, only a sprinkler head, or heads, exposed to enough heat will activate, and no others. A glass vial, filled with a temperature sensitive fluid, keeps a plunger seated in the sprinkler head. The fluid expands and breaks the glass at a specified temperature which allows the water pressure to expel the plunger. You can find out the spray pattern and coverage area by contacting the manufacturer.

With the sharp reduction in smokers, and smoking in bed, the kitchen and dining room are probably your best bets for coverage without the expense of a whole house system. (The CDC also lists improper use of space heaters and unscreened fireplaces as other common causes of house fires.) The water should ultimately cause any electrical ckt to short out and pop the breaker before extinguishing the fire. Water won't put out the oil fire but it will certainly retard the fire's spread. I am still finishing construction on my kitchen and plan to at least rough-in sprinkler coverage for the cooking area.

You may also want to ensure your local building codes allow for partial sprinkler systems. Many areas are now requiring sprinklers in new home construction and they may require complete home coverage if a system is part of a remodeling project (similar to requirements for electrical wiring upgrades).

Your best bet for safe egress is a good system of smoke and CO2 detectors and multiple exit points. Hope this helps...

That was helpful.
When we bought the house there was a fire escape from the third floor. Besides being hideously ugly, it also was located against the windows in a way that it couldn't be attached to the house above the second floor!
We are putting hard-wired smoke detectors in all bedrooms, but would like some extra insurance for those in the third floor bedrooms to have a way out. I figured that if the stairs don't burn that gives us a fighting chance. Those drop-down ladders would work but I think a child would hesitate to use one.
My fire alarms will be hooked up to a central station. The alarm guy has recommended both a smoke detector and a heat detector for the kitchen. Do you think this is redundant?
Thanks.

Your alarm guy is right and I am sure he is talking one detector with both capabilities. There are typically three types of residential detectors -- photoelectric, ionization, & carbon monoxide (CO, not carbon dioxide, CO2, as I wrongly stated before). Dual photo & ion alarms are now recommended. The ion alarms are better at detecting flames (heat) where little smoke is present whereas the photo alarms are more suited to smoldering or smoky fires.

I understand your concern re THE 3RD FLOOR. My childhood bedroom was in the attic and I just had to regularly practice my emergency exit by hanging from my window and dropping onto our flat-roofed garage :o. I'm sure you don't want to pass that info on. The Nat'l Fire Protection Assoc (NFPA) dictates bldg codes for life safety & electrical wiring. Their site, nfpa.org, is a good resource but your local fire dept will be more than happy to help you as well. Talk to them about the 3rd floor issue.

This is a very good thread,

I am curious how one would go about adding a sprinkler system to an existing house without a lot of disruption?

How "safe" are these system? are there a lot of failures?

Sprinklers are required by code in my area. I don't know much about it but I thought I'd share a couple observations. The heads appear to be 8-16 apart, not sure why the distance varies so widely. I do have heads in the kitchen.

When I had a problem with a pressure release valve opening up, regular plumbers would not touch the system. It had to be fixed by the original company which specializes in sprinkler installation. Also just fyi the heads are recessed and covered by flush plastic pop-out panels so the installation is pretty clean.

I havent seen any with the plastic covers over them.. Interesting.. Guess that would make them pretty much invisible.. Do you have a pic?

Well there's not much to show actually. Here's the only pic that I have of the ceiling. There's two sprinkler caps in the photo but you can't really see them.

Well there's not much to show actually. Here's the only pic that I have of the ceiling. There's two sprinkler caps in the photo but you can't really see them.

Re concerns stated by fromplattoplace -- 1) the video below addresses the failure rate & testing of sprinkler heads (although the info is from the UK I am fairly certain the same is done in the US). ; and 2) install is really only economical during new construction or extensive remodeling. Retrofit installs may be kept less expensive with wall, vice ceiling, mounted heads. However, I don't know if there are hidden wall heads similar to the hidden ceiling heads used in chiefneil's home.

I'm guessing here but most plumbers will likely not touch a sprinkler system due to liability issues. If they are not certified for sprinkler systems they would have almost no legal or financial coverage in the event of a malfunction (you touch it you own it - or it owns you). In addition to spot or whole house coverage design there is also the issue of keeping sprinkler water separate from potable (drinking) water. The first fitting on a sprinkler branch off your main water feed is usually a backflow preventer. This prevents the stagnant, and soon undrinkable, water from flowing back into your potable supply. Improper installation of this valve can result in significant health issues. Hence, certified sprinkler installers with, I'm sure, significant liability insurance.

Here are some good sites for homeowner self-education:

http://www.homefiresprinkler.org/Consumer/ConsHome.html
http://video.google.com/videoplay?docid=-3251706666192633226 (this is a very good video from the UK)
http://www.ircfiresprinkler.org/ (addresses code issues)
http://www.toolbase.org/PDF/DesignGuides /express_resi_fire_sprinkler.pdf (a tech doc from the county I previously lived in)
http://www.firesprinklersystemsinfo.com/residential-commercial-firesprinkler-systems.htm (another UK site where this page provides a good overview of facts vs fiction)

fromplattoplace- We actually gutted the house so it's not really being put into existing.
I live in NYC and was not required to put them in, although that might be because I'm renovating an existing 3 story and not building a new one. The laws are different for new construction.
My alarm guy actually recommended a photo smoke detector plus a separate heat activated sensor. I think I'm going to go just with the heat sensor because a kitchen smoke detector is a pain whenever you want to fry something.
I just consulted another alarm guy who seems less inclined to over-protect, so we'll see what he says.
Thanks everyone.