Air Quality: What's In The Air We Breathe?

Air is an invisible mixture of gases that surrounds the Earth, containing essential substances like oxygen and nitrogen that most species need to survive. It is one of the most important factors in sustaining life on the planet, and its quality directly impacts the health and quality of life of humans and other organisms. Air pollution, caused by human-induced climate change, wildfires, and industrial development, poses a significant threat to respiratory health and the environment. Therefore, understanding the importance of air and taking action to protect its quality are crucial for the well-being of all living beings.

Air pressure changes with elevation

Air pressure is the force exerted by the weight of the air piled on top of something. The scientific unit of pressure is the Pascal (Pa), named after Blaise Pascal. One pascal equals 0.01 millibars. The standard pressure at sea level is 1013.25 millibars.

As elevation increases, the number of molecules in the atmosphere decreases, and the density of the air is reduced. This means there is a decrease in air pressure. The higher up you are, the less of the air pillar is above you and more below you, so the air pressure decreases. This is why air pressure on mountains is usually lower than at sea level.

The decrease in pressure with height makes it challenging to compare air pressure at ground level from one location to another, especially when the elevations differ. To address this issue, meteorologists convert the air pressure readings at various stations to values that would be observed if the instrument were positioned at sea level. This conversion ensures a common denominator for comparison.

The variation in atmospheric pressure with elevation has several practical implications. For instance, cooking at high elevations requires adjustments to recipes or pressure cooking due to the lower boiling point of liquids. Additionally, atmospheric pressure measurements have been historically employed to determine the height of hills and mountains accurately.

Air pollution and health

Air pollution has a significant impact on human health. It occurs when harmful substances, such as exhaust fumes from cars, are released into the atmosphere. These pollutants can combine with other elements to form smog, a harmful mixture of smoke and fog, or create clouds of toxic dust. Certain gases, such as methane and excess carbon dioxide, can also contribute to air pollution by disrupting the balance of molecules in the air, leading to global warming.

Ground-level ozone, a common air pollutant, poses a risk to the health of all residents in Colorado, for example. It can trigger asthma attacks and cause acute respiratory issues. Prolonged exposure to ozone can lead to long-lasting lung damage. To protect their health, people are advised to avoid rigorous outdoor activities during periods of high ozone levels, particularly during the heat of the day.

The Air Quality Index (AQI) is a tool used to measure air pollution and communicate the associated health risks. It is calculated by the EPA and categorised into six colour-coded categories, each representing a range of index values. An AQI value of 50 or below indicates good air quality, while a value over 300 represents hazardous air quality. Values above 100 indicate unhealthy air quality, first for sensitive groups and then for everyone as values increase.

Air pollution has both direct and indirect effects on human health. Directly, the inhalation of polluted air can lead to respiratory and cardiovascular problems, with vulnerable individuals, such as those with asthma, being particularly at risk. Indirectly, air pollution can impact human health by contributing to climate change and global warming, leading to extreme weather events and the spread of certain diseases.

Ozone and UV protection

Ozone is a special type of gas molecule found in the Earth's atmosphere. It is made up of three atoms of oxygen and is found in the stratosphere, approximately 15-40 kilometres (10-25 miles) above the Earth's surface. The ozone layer acts as an invisible shield, protecting life on Earth from harmful ultraviolet (UV) radiation from the sun.

UV radiation is a portion of the electromagnetic spectrum with wavelengths shorter than visible light. The sun's UV radiation is commonly split into three bands: UVA, UVB, and UVC. The ozone layer is particularly effective at absorbing UVB radiation, which causes sunburn and, in the long term, can damage the health of humans, animals, plants, and microbes. When an ozone molecule absorbs UVB radiation, it breaks down into an oxygen molecule (O2) and a separate oxygen atom (O). These components can then recombine to form an ozone molecule again.

The ozone layer is constantly being produced and destroyed. Human activities, such as the emission of ozone-depleting substances (ODS), have contributed to the depletion of the ozone layer. ODSs include chlorofluorocarbons (CFCs), which were once commonly found in air conditioners, refrigerators, aerosol cans, and inhalers. Other ODSs include hydrochlorofluorocarbons (HCFCs), halons, and methyl bromide. The depletion of the ozone layer allows more UVB radiation to reach the Earth's surface, increasing the risk of skin cancer, cataracts, and potential damage to marine organisms, plants, and some materials like plastics.

To address ozone depletion, the Montreal Protocol, an international treaty, was implemented to phase out the production of ODSs. As a result, the ozone layer is slowly recovering. Organizations like CAMS (Copernicus Atmosphere Monitoring Service) monitor the ozone layer and provide UV forecasts to help people reduce their risk of overexposure to UV radiation.

Air and fire

Air is essential for life on Earth, providing insulation that regulates the planet's temperature and protecting against harmful ultraviolet rays and meteoroids. The air in the Earth's atmosphere acts as a shield, insulating the planet and preventing extreme temperatures. This protective layer of air also includes ozone, which safeguards Earth from excessive sunlight and harmful UV rays. Additionally, the atmosphere helps burn meteoroids into small pieces before they reach the planet's surface.

However, air is susceptible to pollution, which negatively affects the quality of the air we breathe. Air pollution arises from harmful byproducts, such as exhaust fumes from vehicles, smoke, and industrial emissions. These pollutants can combine with fog to form smog, create toxic dust clouds, and contribute to global warming by upsetting the balance of atmospheric molecules. Forest fires, car emissions, and industrial activities are significant contributors to poor air quality.

To monitor and address air pollution, various tools and measures are employed. The Air Quality Index (AQI) is used to assess and communicate outdoor air quality and its health implications. It is measured on a scale from 0 to 500, with lower values indicating cleaner air and higher values signifying increased pollution and health risks. When the AQI exceeds 100, the air quality is considered unhealthy, particularly for sensitive individuals. Action Days are declared to indicate poor air quality and trigger public health recommendations, driving reductions, and restrictions on indoor burning to mitigate the situation.

Fire, a rapid chemical reaction involving the combustion of fuel and oxygen, is a crucial element in understanding air. Fire relies on the presence of air, specifically oxygen, to sustain itself. The interaction between fire and air can have both positive and negative impacts. On the one hand, fire can serve as a tool for various purposes, including cooking, generating heat, and powering engines. On the other hand, uncontrolled fires, such as wildfires, can contribute to air pollution, releasing smoke and particulate matter into the atmosphere and exacerbating respiratory issues.

In conclusion, air and fire are interconnected, with fire depending on the presence of oxygen in the air for its existence. While fire can be harnessed for beneficial purposes, it is essential to manage it responsibly to prevent negative consequences for air quality and the environment. Understanding the delicate balance between air and fire is crucial for maintaining the health and sustainability of our planet.

Pneumatics and air brakes

Pneumatics is a branch of engineering that makes use of pressurised gas to produce mechanical motion. Pneumatic systems are used in a variety of applications, including air brakes in vehicles.

Air brakes are a critical component of diesel vehicles, such as trucks, buses, and trailers, and are used to enhance vehicle safety. They are also commonly used in railroad trains, especially those with multiple trailers. Air brakes were first developed for trains by George Westinghouse, who patented a safer air brake system in 1872. Before this, trains used a primitive manual brake system that required a brakeman in each car to apply the brakes when signalled by the engineer. Westinghouse's system was designed to mitigate the danger of leaks, a significant problem with hydraulic braking systems. In a hydraulic system, leaks can be difficult to spot, especially in larger vehicles, and if braking control is lost, the consequences are much more severe.

Air brakes use compressed air to apply the service brakes and release the parking brake. When the brake pedal is pressed, pressurised air is released from the storage tank and moves through a valve system to the vehicle's air chambers, causing the brake to be engaged. The parking brake can also be used as an emergency brake. Air brake systems have multiple air circuits to ensure functionality and safety.

While pneumatic systems are more complex and require more space than hydraulic systems, they have several advantages. Pneumatic systems are less likely to run out of operating fluid and are easier to maintain. They are also safer, as a sudden loss of air pressure will result in full spring brake pressure, bringing the vehicle to a stop.

Frequently asked questions