The ingredient of edible oil is complex and its boiling point is not exactly the same. The boiling point of the main components is 300 ℃. The formation process of oil fume and water vapor is as follows
(1) When the cooking oil is heated to 50 ~ 100 ℃, there is a slight rise of hot gas on the oil surface, and the low boiling point components and water are vaporized first.
(2) When the oil temperature rises to 100 ~ 270 ℃, the components with higher boiling point begin to vaporize, and the oil bubbles are dense, formingvisible oil fumes, which are mainly composed of small oil droplets straight above 10 um.
(3) When the oil temperature is higher than 270 ℃, the components with high boiling point begin to vaporize and form a large number of “green smoke”, which is mainly composed of soot particles with a diameter of 3 ~ 10 um. Add food to the oil, and the moisture in the food will expand rapidly. It forms a visible oil mist together with the oil fume.
(4) In the process of rising, the mixture of oil fume and water vapor collides with air molecules, and the temperature drops rapidly, forming aerosol containing condensate, which floats and rises to the surrounding air. The scattered oil fume and steam will form oil and water droplets when they meet the smoke hood, walls, appliances and other objects, polluting the environment. If they are not cleaned up in time, they will produce pollution, mildew, cross pollution and endanger food safety.
Lampblack contains 5 ~ 7 kinds of toxic chemical components, which can stimulate the respiratory tract and lungs of human body. If you work for a long time in this kind of blockage, you will feel depressed, appetite will be reduced, and the heart teacher will be depressed, drowsy, tired, and cough, chest tightness, shortness of breath and other symptoms, serious harm to health.
Lampblack emission brings serious harm to the surrounding residents and the environment. The problem of lampblack pollution in catering industry has become one of the focuses of environmental protection complaints of urban residents.
Kitchen exhaust gas
The kitchen fuel produces waste gas in the process of burning out, which is ejected from the stove mouth or enters the flue. The main components are carbon dioxide, carbon monoxide and steam. The waste gas produced by the stove, lampblack and steam are mixed and scattered in the kitchen, reducing the oxygen content in the air. Carbon monoxide is harmful to human health.
Treatment of polluted air
The kitchen mainly discharges oil fume, steam, waste gas, moisture, peculiar smell, etc. through the comprehensive ventilation and local ventilation system. The comprehensive ventilation is to comprehensively update the indoor air by using natural ventilation and ventilation equipment, and determine the ventilation frequency according to the standard requirements. Local ventilation is to control the diffusion of oil fume, steam, exhaust gas, moisture, peculiar smell and other right gas by using various types of smoke hoods, and use oil fume purifier for purification.
Most kitchen local ventilation is far greater than the total ventilation, so the general kitchen has established a ventilation system based on local ventilation, that is, a smoke exhaust ventilation system based on smoke hood.