In Uk, the Building regulations cover New Build homes primarily, and there are slight differences between those that apply:
+England + Wales
+N Ireland
+Scotland
+Ireland
In England & Wales would also apply if you had a loft conversion done ie making a room in the loft space.
The last government data I saw showed a hard wired % of 13% ie 13% of homes had hard wired alarms; great majority had battery only, with disadvantages that brings.
Some EC countries ie Scandinavia, and US ones permit sealed in battery, or just battery alarms to meet local Regs.
Across UK & Eire there has been steady decline in domestic fire deaths; see data here:
http://www.environ.ie/en/Publications/StatisticsandRegularPublications/FireandEmergencyServices/http://www.odpm.gov.uk/stellent/groups/odpm_fire/documents/divisionhomepage/031597.hcspThe majority of domestic fires are dealt with by homowner, and of course they won't feature in government stats!
What has also driven reduction in deaths is Community Fire Safety thrust of Fire Brigades, allied to government funding for free smoke alarms, initially for the most needy/vulnerable, but increasingly available to anyone who rings up for a free Home Safety Check.
New dangers in the stats, show sources such as candles, which is a reflection on life styles.
US data shows that fires are getting hotter too; see
http://www.kiddefyrnetics.co.uk/utcfs/ws-405/Assets/Home%20Fires%20Hotter.pdfLook at UK web link for more details on sources of ignition.