May Oatway fire alarm, The City

This morning I was looking at the fallow deer grazing peacefully in Richmond Park, when suddenly a red engine with its sirens at full blast whizzed past our windows to attend what looked like a small house fire a couple of streets away.

Originally fire alarm systems were pragmatic and pretty rudimentary. They relied on people spotting the fire and then sounding the alarm with bells, whistles, whatever... However the rapid urban expansion that began in the second half of the nineteenth century required more efficient systems. In the early 1850s two Americans, William F. Channing and Moses Farmer, designed fire alarm boxes with telegraphic keys. Thus the alarm could be raised faster, but the system still relied on human input. Further progress came with heat sensors or thermostats. Between 1873 and 1900 more than thirty different models appeared on the market. Yet these early heat sensors had one major inconvenient: they only triggered the alarm when a preset temperature was reached, usually between 55 and 70 degrees. Thus a low preset temperaure could be safer but would certainly result in false alarms, while a too high one could be fatal. Such a shortcoming was partially corrected by dual detectors, that sent a warning before sounding an alarm if the temperature continued to increase.
An interesting development in fire alarms came in the early twentieth century from the May-Oatway Fire Appliances company. Founded by George Henry Oatway and Charles Edward May, and based at 92-94 Paul Street in the City, it developed a simple and much smaller device that

used a copper wire sensor, the ends of which were connected to a short compensating steel channel fixed to the ceiling. A rapid rise in temperature would cause the copper to expand, and either lower a silvered cone onto electrical contacts or tilt a mercury switch. A gradual rise in temperature would cause both the copper wire and the steel channel to slowly expand in unison and hence the copper would not sag to the same extent. However, the coefficient of expansion of copper is approximately 1.5 times that of steel, and so the detector would switch before excessively high temperatures were reached.
(Robert Bud and Deborah Warner, eds, Instruments of Science: An Historical Encyclopaedia, p. 242)

This fire alarm was patented in the US in June 1906. May-Oatway systems were sold throughout the British empire, and subsidiaries were set up in Australia, New Zealand, and Canada, as well as in the US.
There is very little information available on the web about the company apart from several ads placed in journals roughly between 1900 and the First World War.
At least a painted sign can still be spotted on its London site.

May
Oatway
Fire
Alarm
As for fire alarms, the next stage in their development came in the 1950s with the introducion of the smoke detector.

Location: Paul Street / Picture taken on: 19/04/2008