Air conditioning is a device that uses artificial means to alter the environmental air parameters within a building or its internal environment. In ancient Persia, people used wind catchers installed on the rooftops to allow external wind to pass through cool water, which would be blown into the interior to lower the indoor temperature. This was the precursor to modern air conditioning. With the advancement of science and the enhancement of human knowledge, air conditioning began to utilize various chemical agents, such as Freon, to achieve cooling effects. However, this also led to the destruction of the ozone layer in space and caused environmental damage.

Air conditioning, also known as air regulators, functions by using artificial means to adjust and control the temperature, humidity, cleanliness, and air velocity within a building or its internal environment. Since the discovery of mechanical refrigeration in 1851, over 160 years have passed, during which people have enjoyed the comfort brought by air conditioning while also enduring the pollution caused by air conditioning systems and their impact on human health.

1. Environmental Pollution Caused by Air Conditioning Equipment

1.1 The Destruction of the Ozone Layer by Air Conditioning Equipment

With the popularization of automobiles, car air conditioners have also become indispensable. Nowadays, many vehicle air conditioners use refrigerants like CFC-12, which belong to chlorofluorocarbons. When these chemicals enter the atmosphere and reach the stratosphere, the active chlorine elements cause the destruction and depletion of the ozone layer. Before Freon was restricted, around 20 million tons of Freon were released into the atmosphere globally, causing irreversible damage to the Earth.

1.2 Effects Caused by Air Conditioning Equipment

1.2.1 The Greenhouse Effect

Air conditioning systems are energy-intensive devices, and to supply power to them, a large amount of coal is burned. Additionally, the decomposition of Freon produces a significant amount of greenhouse gases, contributing to the continuous rise in global temperatures.

1.2.2 The Urban Heat Island Effect

In summer, with the extensive use of air conditioning equipment, the amount of CO2 emissions increases, air circulation slows down, and air quality deteriorates. This can lead to poor air quality in factories and other production areas. At the same time, a large amount of heat is released into the atmosphere, causing the temperature in cities to be higher than in suburban areas, residential areas, and plazas.

2. Impact of Air Conditioning Equipment on Human Health

2.1 Bacteria and Virus Growth in Air Conditioning Systems

In over 60 cities in China, nearly 60% of air conditioning systems are severely polluted. Polluted air ducts are found to have accumulated dust and bacteria. The cooling water contains large amounts of microorganisms and bacteria that proliferate. Especially in air conditioners with long-unused filters and evaporators, a large number of mites, pathogens, and mold accumulate. Moreover, people cannot directly see the presence of bacteria, so they tend to neglect cleaning the interior of air conditioners, allowing bacteria and viruses to proliferate. As people breathe in, these pathogens enter the human respiratory system, making individuals susceptible to allergic rhinitis, hypersensitivity pneumonitis, asthma, and other symptoms, including headaches and fatigue.

2.2 Long-Term Use of Air Conditioning and Its Harm to Human Health

In recent decades, with the improvement of technology and living standards in China, more and more households, companies, malls, and restaurants have installed air conditioning systems to adjust the air parameters for greater comfort. However, along with the widespread use of air conditioning comes the severe indoor air pollution in closed environments. Long-term exposure to such environments can cause significant harm to human health. After the air conditioning system operates for approximately 6 hours, the oxygen content in the closed room will drop to around 12.86%. This will lead to an increase in the number of coliform bacteria by 1.35%, and various other bacteria will also grow to different extents. The decrease in oxygen levels and the increase in bacteria have a significant impact on the human body, such as a weakened immune system, insufficient oxygen supply, and the invasion of viruses and bacteria, leading to colds, respiratory difficulties, and other complications. The degree of impact caused by air conditioning depends on how long people stay in the enclosed air-conditioned space. Research shows that the longer people stay, the greater the impact, and this effect seems to increase in parallel with the duration of exposure. To avoid this, the air conditioning temperature should be set within a 6°C range of the indoor temperature, the operation time of the air conditioner should be minimized, and ventilation should be enhanced in closed environments. The air should be circulated with fresh air, the concentration of negative ions in the room should be increased, and air quality should be maintained to reduce the accumulation of harmful substances, ensuring the health of individuals.

3. Development of New Refrigeration Technologies

The increasingly severe environmental problems have drawn global attention. International agreements like the Montreal Protocol and the Kyoto Protocol have been introduced, and countries are actively cooperating. As the largest developing country in the world, China has actively responded to the call for energy conservation and emission reduction, issuing policies such as the Opinions on Accelerating the Development of Energy-saving and Environmental Protection Industries, Ozone Layer Protection Regulations, and Energy Conservation Law, while also providing related government support. The global refrigeration industry has made positive responses as well, with scholars and researchers working tirelessly to explore new environmentally friendly refrigerants and refrigeration technologies.

The repeated use of natural working fluids has significantly reduced environmental pressure. Natural working fluids like air, water, ammonia, and carbon dioxide have a common characteristic: their ODP (Ozone Depletion Potential) and GWP (Global Warming Potential) are all zero, meaning they have no harmful impact on the environment. In the late 1990s, absorption refrigeration technology using water and ammonia as refrigerants was confirmed to be usable, and air was widely adopted as a refrigerant in aircraft. The advantages of carbon dioxide-based systems, such as compactness and high heat exchange efficiency, mean they could potentially replace automobile air conditioning systems in the future. Carbon dioxide-based refrigeration systems used in supermarket freezers have also gained recognition due to their practical cost-effectiveness and reliability.

At the same time, new refrigeration technologies continue to develop. For example, thermoacoustic refrigeration uses the thermal interaction between compressible fluids and solid materials to generate a thermodynamic effect for refrigeration. The basic principle involves sound waves generated by a sound source propagating through a gas medium, generating sound pressure, which causes the gas inside a tube to compress and expand, raising its temperature. This heat is then absorbed by a heat exchange plate, allowing the system to achieve cooling. Thermoacoustic refrigeration is already applied to infrared sensors and other electronic cooling systems and is expected to have great prospects in low-temperature electronic devices due to its low vibration and high reliability. Another technology is thermoelectric refrigeration, which uses the Peltier effect to generate cooling. The cooling effect is determined by the thermoelectric potential of two materials, usually semiconductors. The principle involves electrical charges moving from a high-energy level to a low-energy level, releasing energy, which causes the temperature to drop on one side of the system. Thermoelectric refrigeration has the advantages of simple structure, small size, and quick start-up, making it suitable for small air conditioning systems in vehicles.

Embrace eco-friendly air conditioning solutions today. By adopting sustainable technologies and natural refrigerants, we can reduce environmental impacts and promote a healthier future for both our planet and our well-being.