For a few years now the voice guide announces to passengers that «On board the trains And prohibited make use of cigarettes electronic» because their smoke, “vaping” (which isn't actually smoke, it's aerosols), can activate the system fire prevention. The detectors are a fundamental part of the fire prevention system to which they are connected: in fact, they serve to signal the possible presence of a fire inside the environment in which they are located and to send the signal to the system control unit, all while emitting an acoustic signal. We therefore carried out experiments to discover the effect of the aerosol of an electronic cigarette on different types of smoke detectors: a photoelectric detectora heat detector it's a carbon monoxide detector. E-cigarettes activate detectors of the first type but not the other two. We also took advantage of it to understand how these instruments work from a scientific point of view and discover the physical chemistry behind them.
In the video above we will see:
- an introduction to detectors;
- the experiment with the photoelectric detector;
- the heat detector test;
- the operation of the CO detector;
- final comparison and conclusions.
The effect of e-cigarette aerosol on a photoelectric detector: how it triggers
The photoelectric detector, essentially, uses a laser to detect the presence of aerosol like smoke. It has three main components: one rooma laser it's a optical sensor. The laser aims directly at the optical sensor; if the chamber is empty – or rather, contains only air – the laser passes undisturbed through the chamber and the light beam will always reach the sensor with a certain intensity. However, this device is very sensitive to particles suspended in the air, so when smoke or an aerosol enters the device, the sensor perceives the laser at a lower intensity, because the smoke particles scatter the light from the laser.
This phenomenon is called Tyndall effect and it is the same phenomenon that happens for example in discos or on concert stages: the machines “shoot” white smoke (even in this case they should actually be called aerosol machines, not “smoke machines” as they are commonly known), which disperses the light of the stage lasers making them visible. So yes, this type of detector will be activated with any type of cigarette, and is effective both in the presence of smoke (aerosol solidformed by solid particles dispersed in the air) that of I vape (aerosol liquidformed by liquid particles dispersed in the air).
These detectors are those that are most frequently used in public fire systems, such as on trains, in stations, in shopping centres, but also in domestic ones, often coupled with other types of detectors, such as heat detectors.
The effect of e-cigarette aerosol on a heat detector: when it goes off
This type of detector is not used alone, because it would not be sufficient to enable timely intervention in the event of a fire, because it is alarmed only if the environment reaches a certain temperature which varies depending on the appliance. In our case it is 57°Cand we tested it by heating water until it generated steam at a slightly higher temperature.
Therefore the heat detector could be activated even without the presence of an actual fire, especially in environments where there may already be high temperatures, for example an engine room, a server room or more commonly in a kitchen. So, although this type of detector will certainly never be alarmed by the aerosol of an electronic cigarette or the smoke of a traditional cigarette, if there is a heat detector, there is probably also one nearby for detecting smoke ( such as, precisely, the photoelectric) or for the carbon monoxide.
The effect of e-cigarette aerosol on a carbon monoxide detector
This instrument detects a substance, the carbon monoxide (CO), which develops during fires and is therefore only present in the smoke resulting from a combustion. Monitoring the concentration of carbon monoxide could be useful if you have a chimney or one heater, this is because, if they are not used correctly, they could develop carbon monoxide. And carbon monoxide is toxic at high concentrations: for example, two hours of exposure to an environment with a concentration of carbon monoxide above 1600 ppm (parts per million) could lead to death. This is because carbon monoxide easily binds tohemoglobin, which would therefore no longer be able to transport oxygen. This type of detector is essential in environments with stoves or fireplaces, since CO is odorless and colorless but highly toxic.
But, returning to our experiment: is the carbon monoxide detector activated by the electronic cigarette? What about heated tobacco cigarettes? The answer is no, as neither in the electronic cigarette nor in the heated tobacco cigarettes does combustion take place, consequently in neither of the two aerosols produced following a “vape” is carbon monoxide present.
Traditional cigarettes are an exception: we can imagine lighting a cigarette as starting a small fire, it will therefore be easy to remember that a combustion reaction occurs and, therefore, of the presence of carbon monoxide in cigarette smoke.
