Smoke detector

[6] He expected the gas entering the sensor to bind to ionized air molecules and thereby alter an electric current in a circuit of the instrument.

[7] In 1939, Swiss physicist Ernst Meili devised an ionization chamber device capable of detecting combustible gases in mines.

[8] He also invented a cold cathode tube that could amplify the small signal generated by the detection mechanism so that it was strong enough to activate an alarm.

[10] In 1963, The United States Atomic Energy Commission (USAEC) granted the first license to distribute smoke detectors that used radioactive material.

The photoelectric (optical) smoke detector was invented by Donald Steele and Robert Emmark from Electro Signal Lab and patented in 1972.

In spot-type detectors, all of these components are arranged inside a chamber where air, which may contain smoke from a nearby fire, flows.

If the air in the chamber contains particles (smoke or dust), the light is scattered and some of it reaches the sensor, triggering the alarm.

Some Russian-made smoke detectors, most notably the RID-6m and IDF-1m models, contain a small amount of plutonium (18 MBq), rather than the typical 241Am source, in the form of reactor-grade 239Pu mixed with titanium dioxide onto a cylindrical alumina surface.

A person would have to open the sealed chamber and ingest or inhale the americium for the dose to be comparable to natural background radiation.

The government of New South Wales, Australia considers it safe to discard up to 10 ionization smoke detectors in a batch with domestic rubbish.

[32] Some European countries, including France,[33] and some US states and municipalities have banned the use of domestic ionization smoke alarms because of concerns that they are not reliable enough as compared to other technologies.

Clause 3.0 states, "Ionization smoke alarms may not operate in time to alert occupants to escape from a smoldering fire.

"[36] In May 2011, the Fire Protection Association of Australia's (FPAA) official position on smoke alarms stated, "The Fire Prevention Association of Australia considers that all residential buildings should be fitted with photoelectric smoke alarms..."[37] In December 2011, the Volunteer Firefighter's Association of Australia published a World Fire Safety Foundation report, "Ionization Smoke Alarms are DEADLY", citing research outlining substantial performance differences between ionization and photoelectric technology.

[38] In November 2013, the Ohio Fire Chiefs' Association (OFCA) published a position paper supporting the use of photoelectric technology in Ohioan residences.

"[39] In June 2014, tests by the Northeastern Ohio Fire Prevention Association (NEOFPA) on residential smoke alarms were broadcast on ABC's Good Morning America program.

The NEOFPA tests showed ionization smoke alarms were failing to activate in the early, smoldering stage of a fire.

[42] Due to the varying levels of detection capabilities between detector types, manufacturers have designed multi-criteria devices which cross-reference the separate signals to both rule out false alarms and improve response times to real fires.

[47] Between 2005 and 2007, research sponsored by the United States National Fire Protection Association (NFPA) focused on understanding the cause of the higher number of deaths in such high-risk groups.

Research findings suggest that a mid-frequency (520 Hz) square wave output is significantly more effective at awakening high-risk individuals.

In response public information campaigns have been created to remind people to change smoke detector batteries regularly.

In Australia, for example, a public information campaign suggests that smoke alarm batteries should be replaced on April Fools' Day every year.

[51] On the night of May 31, 2001, Bill Hackert and his daughter Christine of Rotterdam, New York, died when their house caught fire and a First Alert brand ionization smoke detector failed to sound.

[52] The cause of the fire was a frayed electrical cord behind a couch that smoldered for hours before engulfing the house with flames and smoke.

The United States NFPA code, cited earlier, requires smoke detectors on every habitable level and within the vicinity of all bedrooms.

[56] The resulting increase in current flow (or a dead short) is interpreted and processed by the control unit as a confirmation of the presence of smoke and a fire alarm signal is generated.

[56] Addressable systems are usually more expensive than conventional non-addressable systems,[58] and offer extra options, including a custom level of sensitivity (sometimes called Day/Night mode) which can determine the amount of smoke in a given area and contamination detection from the FACP that allows determination of a wide range of faults in detection capabilities of smoke detectors.

This standard expands on the EN54 recommendations for domestic smoke alarms and specifies requirements, test methods, performance criteria, and manufacturer's instructions.

[10] In 1988 BOCA, ICBO, and SBCCI model building codes begin requiring smoke alarms to be interconnected and located in all sleeping rooms.

This was further to the Australian Government's scientific testing agency (the Commonwealth Scientific and Industrial Research Organisation – CSIRO) data revealing serious performance problems with ionization technology in the early, smoldering stage of a fire, a rise in litigation involving ionization smoke alarms, and increasing legislation mandating the installation of photoelectric smoke alarms.

Some manufacturers may also cooperate with law enforcement agencies, potentially providing them with access to users' data without their knowledge or consent.