There is a New California State Law regarding Carbon Monoxide Detectors.

First of all, what is Carbon Monoxide?   Carbon Monoxide is also called Carbon Oxide (CO).  It is a colorless, odorless, and tasteless gas which is slightly lighter than air.  It is highly toxic to humans and animals in higher quantities.  Carbon Monoxide is produced whenever any fuel, such as gas, oil, kerosene, wood, or charcoal, is burned.  Symptoms of carbon monoxide poisoning are often mistakenly diagnosed as the flu.
The new Carbon Monoxide Poisoning Prevention Act (Senate Bill 183) requires owners of all existing single family homes with an attached garage or a fossil fuel source, to install a CO alarm device by July 1, 2011. Owners of multi-family leased or rental homes, such as apartment buildings have until January 1, 2013 to comply with the law.
So what is a Carbon Monoxide Detector?

A Carbon Monoxide Detector is very similar to a smoke detector but it produces a very distinct audible alarm when it detects carbon monoxide in the air.   They are not very expensive - usually around $20.00.   This great device can be battery powered, a plug-in device with a battery backup, or a device installed as recommended by Standard 720 of the National Fire Protection Association that is either hard-wired into an alternate power line with a secondary battery backup or connected to a system via a panel.

How many do I need to put in my home?

The new law requires the owner to install the devices as if they were buying a new-build today (consistent with building standards applicable to new construction for a similar home).   They should be installed outside each sleeping area and on every level of the home, according to the Fire Marshal's Office.   If it is not done, you can be fined up to $200.00 for each offense.   (A property owner must receive a 30 day notice to correct first).

Do Landlords have any special obligations regarding Carbon Monoxide Detectors?

Yes.  All landlords of dwellings must install the detectors.  The law gives the landlord the authority to enter the house or units for the purpose of installing, repairing, testing, and the maintaining the detectors.  They must be operational when the tenant takes possession.