Professor Dr. Nguyễn Đức Lợi from the Refrigeration Science and Technology Association stated that air conditioning and refrigeration systems contain a vapor compressor. The refrigerant gas is drawn from the evaporator by the compressor, which compresses it to a high pressure before pushing it into the condenser. In the condenser, the heat is expelled to the cooling medium, causing the gas to condense into a liquid.
Health Concerns When Surrounded by Air Conditioners
The liquid refrigerant is then passed through a throttling valve into the evaporator. As it passes through the valve, the pressure suddenly drops very low, causing the liquid to evaporate vigorously at low temperatures within the evaporator, resulting in a cooling effect to cool the room.
There are many different types of refrigerant gases. Throughout the history of refrigeration technology, scientists have experimented with thousands of different refrigerants, among which hundreds have been practically applied, including both organic and inorganic compounds.
Among the most representative organic compounds are freons and ammonia for inorganic compounds. Freons are saturated and unsaturated hydrocarbons such as CH4 and C2H6, where hydrogen atoms are partially or completely replaced by chlorine and fluorine atoms. For example, the refrigerant used in refrigerators, R12, is CCl2F2, and the refrigerant for air conditioners, R22, is CHClF2.
Air conditioners are increasingly used, especially in densely populated urban areas.
Professor Dr. Nguyễn Đức Lợi indicated that most refrigerants are non-toxic except for ammonia. Only when there is an excessive amount of refrigerant in the air (about 0.44 kg of refrigerant per 1m3 of air) can asphyxiation occur due to a lack of oxygen. The amount of refrigerant in a refrigerator is about 0.1 kg, while in a 3.5 kW (12,000 Btu/h) air conditioner, it is approximately 1.0 kg. If a room has an area of 20m2 and a height of 3m (60m3), it would require the refrigerant from 260 refrigerators or 26 air conditioners to pose a risk of asphyxiation to people.
However, it is important to note that in the presence of iron and steel as catalysts, freons decompose at 550 degrees Celsius, producing highly toxic phosgene. Refrigeration technicians need to be especially cautious when using blowtorches to repair air conditioning and refrigeration units. Ammonia is very toxic, causing irritation to mucous membranes, eyes, and stomach, leading to respiratory spasms and skin burns; however, it has a pungent odor that makes it easy to avoid. Ammonia gas is only used in large industrial refrigeration and is not found in domestic refrigeration, making it less common.
Refrigerant Gases: An Environmental Threat
Professor Dr. Nguyễn Đức Lợi explained that freon gases R12 and R22 are non-flammable and non-explosive, but due to the harmful impact of many traditional freons on the ozone layer, newer types of freon must be used today. However, these new types are not entirely safe compared to traditional freons. To protect the environment and eliminate R12, some countries in the European community, India, and others are using butane and propane cooking gases to charge refrigerators. These substances pose a very high risk of explosion. Although the charge is only 0.1 kg per refrigerator, if air mixes with it and there is an electrical leak, it can create a spark, turning the refrigerator into a bomb. Therefore, safety measures for these types of refrigerators are particularly important.
The mechanism by which refrigerant gases destroy the ozone layer lies in the chlorine component of freon gases, which is the main culprit in ozone depletion. When refrigerants leak into the atmosphere, they are very stable but gradually rise to the stratosphere, approximately 10-15 km above the earth’s surface. Under the influence of ultraviolet rays, they decompose into chlorine atoms.
These chlorine atoms break down ozone into O2 and single oxygen atoms O. Each chlorine atom can destroy tens of thousands of ozone molecules. Freons that do not contain chlorine do not deplete the ozone layer. For example, new freon types include R134a (C2H2F4), R410A, R407C, and R507.
“The greenhouse effect, also known as global warming, is the phenomenon where gas traps long-wavelength thermal radiation from the Earth into space, causing the Earth to heat up. This effect is similar to a solar energy collection box with a glass cover on top. Short-wavelength solar radiation can easily pass through the glass and is absorbed by the black-painted surface inside. Although the black-painted surface has a high temperature, it is much lower than the sun’s temperature, so it only radiates back as long-wavelength thermal rays.
These rays cannot pass through the glass and are reflected back, causing the temperature inside the box to rise. The gas primarily responsible for this greenhouse effect in the atmosphere is CO2. The CO2 levels from volcanic activity, forest fires, etc., are considered balanced. However, in recent years, CO2 levels have significantly increased due to human activities from fuel extraction and consumption, along with the emission of millions of tons of refrigerant gases into the atmosphere.
Refrigerant gases often have greenhouse effects thousands of times greater than CO2, with some freons being up to 3000 times more potent. The higher the number of fluorine atoms in freon, the greater the greenhouse effect. Therefore, it is imperative to prohibit the release of refrigerant gases into the atmosphere for any reason,” shared Professor Dr. Nguyễn Đức Lợi.
Among the refrigerants, R12 and R22 were previously considered ideal. However, R12 is now banned due to its ozone-depleting properties, and R22 will also be banned by 2030 (with a deadline for Vietnam set for 2040). Regrettably, to date, scientists have been unable to find a feasible replacement for R12 and R22 that does not adversely affect the environment.
