I'm starting this new thread as I don't want to take the gun sites thread off topic.
Jimbob and I remember these during the war. They were a defence against enemy bombing, obscuring the target area. I remember them being placed along Borough Rd. opposite the Rovers' ground, but I don't remember having seen one in operation. I'm pretty sure Jimbob did though.
Here's a little bit of info. I found, but I'm hoping someone may be able to find something in the Archives, since I'm pretty sure the local authority would have been in charge of them.
Turbine Technologies Ltd History
The concept of military smoke screening dates back hundreds of years. One of the earliest documented uses of smoke screen in combat was the burning of green vegetation by the Romans and later the burning of peat moss by the Vikings. In the American Civil War, General Robert Schenck burned wet tree limbs and leaves to create a smoke screen to cover his retreat. In all of these early smoke screen attempts, the method employed was direct flame contact with combustible material.
These combustion methods were a bit uncontrollable and had only limited advantages in combat. Generally, they could only be used to conceal troop numbers or to cover a retreat but could not effectively be used in covering troop advances due to the effect of smoke on the advancing troops. In addition, because smoke is lighter than air, the smoke cover was only temporary and large volumes of smoke were necessary to create sufficient cover. Thus a sizable amount of time was required to ignite and burn the material.
World War II
British forces used large area smoke screens to protect their towns, cities and industrial centres from the German Bombing during 1940 / 1941.
British military leaders realized they could not fend off the massive attacks of the Germans but learned they could protect their assets by hiding them from the German bombers. Prior to 1941, German bombing campaigns were very effective against British cities. Reacting to lessons learned from the past, British forces were familiar with the concept of large area smoke screening. Twenty years earlier, during World War I, the British successfully used smoke and obscurants to conceal their own operations during the Battle of Jutland. Massive German bombing campaigns would have devastated the British forces, and the British knew they had to take measures to conceal their most vital assets with visual obscuration. One method the British used to protect their industrial centres involved the use of smoke pots and British civilians. Under the Civilian Defence Program, civilians living near industrial complexes would come out during alerts and ignite smoke pots pre-positioned in the area. A massive smoke build up occurred once the pots were ignited, which resulted in huge smoke clouds covering the industrial centres. The smoke clouds prevented the German bombers from locating their targets.
In the early morning of 7 July 1943 the port, lake, channel, outer harbour and bay at Bizerte were crowded with US ships concentrated for the impending Allied invasion of Sicily.
Around 4 a.m. on 7 July, approximately 60 German aircraft launched an attack on the port areas of Bizerte. Though the attack lasted for more than half an hour, German airplane pilots could not locate their targets. Just minutes before German planes descended upon Bizerte, US forces used smoke generators to create a dense fog over the area. Within the screened area, not one bomb hit its target, nor was a single ship damaged.
The enemy raid on Bizerte failed primarily because of the blanket of oil smoke US troops made using the M1 mechanical smoke generator. The M1 generator was the first mechanical generator used for large area smoke and obscurant screening by US forces during World War II. While the use of smoke operations was gaining momentum, the M1 was not even on the drawing boards at the beginning of the war. The M1 smoke generator was quickly fielded in 1942 to save lives and equipment for situations such as Bizerte.
The "smoke" created by today's technology is neither a smoke (like the product of a combustion smoke screen) nor a chemical gas (like the product of a chemical smoke bomb) but was a vapour of a specially designed oil. This 'Fog Oil' is atomised in the exhaust duct of a small gas turbine engine using a specially designed nozzle. Exposed to a temperature of some 600°C the atomised oil evaporates instantly. On exiting the exhaust the oil condenses into a vapour that provides a long-lasting, ground hugging, obscuration cloud.