An allergen is a substance that can cause an allergic reaction by triggering the body’s immune system. Common indoor allergens include dust mite droppings, pet dander, mould and pollen.

A common name for a visible group of fungi, mould thrives wherever there is dampness – sending out millions of spores into the air. Exposure to mould occurs via inhalation, skin contact or ingestion. 

Microscopic, single-celled organisms that exist in their millions, in every environment. Not all bacteria are harmful, but some can have adverse effects, such as E. coli.

Benzene is colourless, flammable liquid produced by both natural and man-made processes. It’s a natural part of crude oil, gasoline, and cigarette smoke. Indoors, it comes from products such as glues, paints, furniture wax, and detergents. 

A colourless greenhouse gas, which comes from the extraction and burning of fossil fuels. Increased CO₂ levels can impact cognitive function.

House dust mites are tiny insects that commonly live in household dust. They are one of the biggest causes of allergies. Each gram of house dust contains approximately 1000 dust mites. 

Formaldehyde is often associated with the familiar smell of fresh paint, or the unboxing of new furniture. It's a colourless, flammable and potentially harmful gas used in some building materials and household products. Sources can include fabrics found in flooring and furniture, glues, paints, varnishes, air fresheners, and household cleaners. 

This subtype of Influenza A virus, also known as swine flu, caused a global flu outbreak. H1N1 produces respiratory infectious diseases in humans and pigs. Symptoms can be similar to seasonal flu.

HEPA (High Efficiency Particulate Air) is an air filter efficiency standard and a measure of a filter’s performance. For an air filter to be classified as HEPA, it must be capable of removing at least 99.95% (ISO, European Standard) or 99.97% (ASME, U.S. DOE) of particles whose diameter is equal to 0.3 microns.

HEPA H13 is an even higher tier of HEPA air filtration efficiency. To meet HEPA H13 standards, a filter must be able to remove 99.95% (ISO, European Standard) or 99.97% (ASME, U.S. DOE) of microscopic particles at the most penetrating particle size of 0.1 microns.

A process of increasing air moisture content through the addition of water vapour or steam. Humidifiers can add moisture to the air in dry conditions, creating a more comfortable indoor environment. 

Airborne particles are usually described in microns. One micron is equal to one-thousandth of a mm. The human eye struggles to see anything smaller than 25 microns in size. Allergens are microscopic. The size of dust mite allergens, mould spores and other insect allergens is often between 0.5 to 5 microns. To provide context, the diameter of a human hair is around 50 microns.

Nitrogen dioxide is a liquid below 21.2 °C and a gas at higher temperatures. It is toxic to humans in both states. Gas stoves and space heaters are the most common indoor sources of NO₂  emissions. Other sources include improperly vented furnaces and water heaters. 

Pet dander is made up of tiny particles of skin, saliva and urine, shed by animals with fur or feathers. Pet dander lingers in the air before settling on surfaces such as furniture, bedding, and fabrics. Exposure to these airborne particles can trigger allergies. 

PM stands for particulate matter, which consists of microscopic solid or liquid particles and pollutants. PM is often followed by a number, which represents the size of the particulate matter in microns (a micron is one-thousandth of a mm). For example, PM01 means particulate matter that is 0.1 of a micron in size. PM2.5 equals particles that are 2.5 microns in size, and PM10 means particles up to 10 microns in size. Indoor PM can be generated through many day-to-day activities, including cooking, cleaning and the burning of candles and fires. 

Pollen is a powdery substance released from seed plants as part of their reproduction process. It typically appears from trees in the spring, grasses in the summer, and weeds in the autumn. Pollen grains are among the most common allergens.

The process of making something free of any contaminants or physical impurities. Air purification is designed to filter the air in your home – removing pollutants such as dust, allergens and viruses. 

SCO is an abbreviation for Dyson's Selective Catalytic Oxidisation filter, a specific type of filter engineered to capture and destroy formaldehyde at the molecular level. Dyson SCO filters break the pollutant down into tiny amounts of water and CO₂. Our filter then naturally regenerates from the oxygen in the air, so it can keep destroying formaldehyde continuously, without ever needing to be replaced.

Volatile organic compounds are potentially harmful gases found in many household products. Common sources include paints, varnishes, air fresheners, cosmetics, and cleaning products.