Smoke detection system in Aircraft

What are the methods to find smoke prevailing in aircraft? Explain with neat sketches.

For smoke, fire is main reason. In some cases it may not be. However pure air just contains 78% of nitrogen, 21% of oxygen and 1% rest of other gases. When there is fire in the aircraft the air will be dirt since carbon monoxide or carbon dioxide presents. There are four effective ways to identify the smoke.

Light detection

Light Refraction

Ionization

Solid state semiconductor

Light detection type:

We all know photo voltaic cell converts light energy into electrical energy. The pure light rays will be fall on photo voltaic panel and produces some electrical energy at normal. 

When the area is surrounded by smoke the intensity of light rays falling on the panel gets differ. From that we get alarm.

Light Refraction type smoke detector:

Here a certain mass of air is taken for smoke detection by use of fan. Source of light is the Electric bulb. It is made to pass it rays from a single point in order to satisfy our requirement. 

The light which fall on the wall of the detection chamber gets reflected and the reflected rays which falls on photo voltaic panel induces some current based on the intensity of rays fallen. When smoke particles comes into picture, they itself reflect the rays before colliding by the wall and makes different electrical energy by making different intensity, thus alarm gets activated.

Ionization type smoke detector:

The Radioactive material (Americium) emits Alpha rays continuously. The Alpha rays makes reaction with the clean cabin air (under normal conditions) and ionize the incoming air ingredients to Positive and Negative charges. 

Those Positive charged ions are attracted by negative charged pole, and Negative charged ions are attracted by positive charged poles. Thus it gives some reading. When smoked air comes into picture the amount of attraction on poles varies and thus we are getting smoke detection alarm activated. 

Solid State Smoke Detector:

A solid filament coated with semi-conductor material is along the length of the fuselage to detect the fire. An electrical current is given over the filament by the wrap around coils. At normal conditions the filament will have some resistance and it produces some output value. When smoke comes into picture, the semi conductor has ability to absorb carbon particles, so that resistance of the filament varies, thus getting different output from that of we got on normal.

 If suppose the atmospheric air itself getting too much carbon particles, then we may  commit a false smoke warning, so that in order to activate alarm we are just comparing the filament exposed to atmospheric air and cabin.