You should install a carbon monoxide detector regardless of what the code says!
http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning:
Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect.
The initial symptoms of acute carbon monoxide poisoning include headache, nausea, malaise, and fatigue. These symptoms are often mistaken for a virus such as influenza or other illnesses such as food poisoning or gastroenteritis. ... Increasing exposure produces cardiac abnormalities including fast heart rate, low blood pressure, and cardiac arrhythmia; central nervous system symptoms include delirium, hallucinations, dizziness, unsteady gait, confusion, seizures, central nervous system depression, unconsciousness, respiratory arrest, and death.
Detectors are cheap ($15-$60) and readily available. They come as battery-operated, plug-in, and as combination smoke/CO detectors. I recently replaced the smoke detectors in my house (which were 10 years old and thus at end-of-life) with these combo hardwired units: they are linked, so if one goes off, they all do, and announce "Fire" or "Carbon monoxide".
Bottom line: If you have a fuel-burning appliance (furnace, stove, etc), fireplace, or attached garage, you should have at least one CO detector.
As far as current compliance, the IRC and local building codes typically only apply to new construction or renovation. For example, if you are doing an addition to your house or other type of permit-requiring renovation, you'll have to comply with the building codes for at least that portion. This may vary by jurisdiction, and there may be other specific laws or regulations that require retroactively complying with the codes. I am just a random person on the internet; you should consult with your local permit office and/or building inspector to know for sure.
Your insurance or mortgage company may also have other requirements, on top of local building codes and law.
Law in US
Since July 1, 2009, Colorado requires CO detectors in all new homes and any re-sold homes.
Since Feb 22, 2010, New York state requires at least one CO detector on the lowest story having a sleeping area. Homes built after Jan 1, 2008 must have a hardwired CO alarm.
Since Jan 1, 2011, California requires CO alarms for new homes, and since July 1, 2011 for existing homes.
Law in Canada
In Ontario, homes built after Aug 6, 2011 must have hardwired CO detectors installed. Legislation was passed in Nov 2013 to require CO detectors in all homes with fuel-burning appliances.
Short answer: Maybe
Here is why: The cable may be rated for 300 volts but it is not #14 gauge minimum size for power and lighting as stated here:
(A) Minimum Size of Conductors. The minimum size of conductors shall be as shown in Table 310.106(A), except as permitted elsewhere in this Code
Table 310.106(A) shows the minimum size to be #14 gauge wire.
However, if you get a 7 amp breaker or fuse marked for use with #18 ga wire or a special class of fuse, you could use this section
Article 240.4(D)(1) 18 AWG Copper. 7 amperes, provided all the following conditions are met:
(1) Continuous loads do not exceed 5.6 amperes. (2) Overcurrent protection is provided by one of the following: a. Branch-circuit-rated circuit breakers listed and marked for use with 18 AWG copper wire b. Branch-circuit-rated fuses listed and marked for use with 18 AWG copper wire c. Class CC, Class J, or Class T fuses
This would be very strange in a house though so your inspector may not want to allow it.
Good luck!
Best Answer
In a single family dwelling, it would be best to use regular smoke alarms. Pick a brand that also sells an interconnect relay, and you can use that to connect it to your security system.
To answer your question, yes you should be able to use low voltage smoke detectors as long as the central control panel has a battery backup and the overall system functions similarly to a normal system. If the smoke detectors don't have a built-in audible notification device, then you'll also need to install one of those in each required location.
Drawing up a building plan to show the Fire Marshal your proposed fire & life safety plans will be an important step. Getting that plan approved will help make sure you don't purchase and install a bunch of equipment that doesn't pass their interpretation of the code.
Usually you would only go through this much extra work if you wanted addressable smoke detectors, but in a single family dwelling that's an extra expense that's not needed in my opinion. That level of system is usually only needed in a commercial or multi-family setting.
In a commercial or multi-family setting, you'll usually want strobes and horns in public areas, horns in each unit, pull stations in the hallways, and the central monitoring station to be able to tell the first responders exactly which zone or location triggered the alarm. In a a single family dwelling, you should be able to easily locate what area needs attention without those features. Regular smoke alarms typically have latching alarm indicators, so it helps you diagnose problems by letting you know which device triggered the alarm.