Millthorpe

PM2.5 are fine particles in air with a diameter of 2.5 micrometres or less. PM itself is short for 'particulate matter', another term for particles. They are generated by combustion processes from sources such as vegetation fires, motor vehicles and industrial activities. PM2.5 is reported in unit of microgram per cubic meter (µg/m³).

These small particles can get deep into the lungs and be absorbed into the blood stream. Short term impacts include difficulty in breathing and worsening of asthma or chronic bronchitis symptoms. They can also cause irritation of eyes, nose and throat.

PM10 are particles in air with a diameter of 10 micrometres or less. PM itself is short for 'particulate matter', another term for particles. They can include dust or sea salt, as well as smaller particles generated from combustion processes such as vegetation fires, motor vehicles and industrial sources. PM10 is reported in unit of microgram per cubic meter (µg/m³).

These particles can pass into the lungs. Short term impacts include difficulty in breathing and worsening of asthma or chronic bronchitis symptoms. They can also cause irritation of eyes, nose and throat.

Visibility here refers to visibility reduction in air due to existence of particles. This is different from visibility measurements obtained by weather stations.

Our visibility measurements are obtained using instrument called 'nephelometer', which measures the scattering from a beam of light by the particles present in the air. Before measurement is taken the air sample is heated so that fog does not impact these measurements. The higher the measurement, the more that air particles are reducing the visibility at that location.

Readings from the instrument are reported in units of 10^-4m^-1 (or 100 inverse megametres). No air quality categories are applied to visibility measurements.

Ammonia is a colourless volatile gas with a pungent odour. It is emitted from both natural and human sources, such as decaying organic matter like animal waste, landfills, fertilisers and industrial production. Its chemical formula is NH₃. Concentrations are reported as parts per hundred million (pphm).

Ammonia is monitored at the Stockton station in the Lower Hunter region. No air quality categories are applied to ammonia measurements.

Nitrogen dioxide is a brown gas that at high concentrations has an irritating odour. It is often found at its highest concentrations near busy roads and can also be high indoors when un-flued gas appliances are used. Its chemical formula is NO₂. Concentrations are reported as parts per hundred million (pphm).

Nitrogen dioxide at higher concentrations is a respiratory irritant which can worsen the symptoms of existing respiratory illness. It also makes people with asthma more susceptible to lung infections and asthma triggers like pollen.

Carbon monoxide is an odourless and colourless gas.. It is produced by incomplete combustion, where there is no sufficient oxygen present to form carbon dioxide. The major sources are motor vehicle exhaust and vegetation fires. Its chemical formula is CO. Concentrations are reported as 8-hour rolling averages in parts  per million (ppm).

Carbon monoxide at higher concentrations can enter the bloodstream through the lungs and inhibits transport of oxygen by blood. People suffering from heart disease are most at risk and may experience chest pain from CO exposure particularly while exercising.

Sulfur dioxide is a colourless gas with a sharp odour. The main sources are fossil fuel combustion, particularly at power plants and mineral ores smelters. Its chemical formula is SO₂. Concentrations are reported as parts per hundred million (pphm).

Sulfur dioxide at higher concentrations can irritate the eyes, nose, throat and lungs. It may worsen existing cardiovascular or respiratory illnesses, such as asthma.

Ground-level ozone is a colourless gas. It is formed by chemical reactions in the atmosphere between volatile organic compounds (VOCs) and nitrogen oxides in the presence of sunlight. Its chemical formula is O₃, Concentrations are reported as parts per hundred million (pphm).

Elevated ozone levels can cause irritation and inflammation of eyes, nose, throat and lower airways. It can affect lung function and worsen asthma. You may notice difficulty in breathing, coughing, and throat irritation if you are exercising outdoors when ozone levels are high.

Ground-level ozone is a colourless gas. It is formed by chemical reactions in the atmosphere between volatile organic compounds (VOCs) and nitrogen oxides in the presence of sunlight. Its chemical formula is O₃.

A longer averaging period of 4-hours is used as a second measure for ozone, reported as parts per hundred million (pphm), indicating the impacts that sustained elevated concentrations can have.

Elevated ozone levels can cause irritation and inflammation of eyes, nose, throat and lower airways. It can affect lung function and worsen asthma. You may notice difficulty in breathing, coughing, and throat irritation if you are exercising outdoors when ozone levels are high.

Horizontal wind is measured at some stations, reported as hourly average in metre per second (m/s). Wind speed represents the rate or speed at which air is moving. The average wind speed is expressed in metres per second. To convert this to kilometres per hour, multiply the reading in metres per second by a factor of 3.6.

Horizontal wind is measured at some stations, reported as hourly average in degrees (^o). Wind direction represents the direction the wind is blowing from, according to the compass. It is labelled following meteorological conventions, such as NW for north-westerly or S for southerly, indicating where the wind was coming from. The arrow on the wind direction plot shows the direction the wind is moving towards.

Ambient air temperature is measured at some stations, expressed as hourly average in degrees Celsius.

Relative humidity is measured at some stations, expressed as hourly average in percentage (%). These refer to the amount of moisture in the air as a percentage of the amount the air can actually hold. Warmer air can hold more moisture than cooler air, which means that for a given amount of atmospheric moisture, Relative humidity will be lower if air is warm than it would be if the air is cool.