Particulate matter (PM) refers to tiny particles or droplets suspended in the air, which can vary in size. It is commonly found in the home from sources such as tobacco smoke, cooking (especially frying or grilling), burning candles, and heating systems like wood stoves. These particles can also come from dust, pet dander, mold, or smoke from wildfires.

Particulate matter is dangerous to humans because when inhaled, the tiny particles can penetrate deep into the lungs, and even enter the bloodstream. This can lead to respiratory problems, heart disease, aggravated asthma, and other serious health issues, especially for children, the elderly, and those with pre-existing health conditions.

Volatile Organic Compounds (VOCs) are a group of chemicals that easily evaporate into the air at room temperature. They are commonly found in household products like paints, cleaning supplies, air fresheners, varnishes, rugs, and even some furniture and building materials. VOCs can also be released from gas stoves.

These compounds are dangerous to humans because they can irritate the eyes, nose, and throat, and long-term exposure to high levels can lead to more serious health issues, including headaches, dizziness, liver damage, and respiratory problems. Some VOCs are even linked to an increased risk of cancer, making proper ventilation and reducing exposure crucial for health.

Carbon monoxide (CO) is a colorless, odorless gas produced by the incomplete combustion of fuels like gas, wood, or charcoal. It can be produced by household appliances that burn fuel, such as gas stoves, ovens, fireplaces, water heaters, and space heaters. Additionally, carbon monoxide can build up in attached garages if a car is left running, or from faulty chimneys or ventilation systems that prevent proper airflow.

This can lead to symptoms like headaches, dizziness, confusion, and even death in high concentrations. Since it's hard to detect without special equipment, carbon monoxide is especially hazardous in enclosed spaces with poor ventilation.

Carbon dioxide (CO₂) is a colorless, odorless gas that is naturally present in the air and produced by human activities like breathing, cooking, and burning fossil fuels. In the home, it can be found in indoor air, especially when using gas stoves, fireplaces, or heating systems, or when there is poor ventilation.

While CO₂ is not toxic at normal levels, elevated concentrations can be dangerous. At high levels, it can displace oxygen in the air, leading to suffocation, dizziness, and confusion. Prolonged exposure to elevated CO₂ can be harmful to health, particularly in poorly ventilated spaces.

Sulfur dioxide (SO₂) is a colorless, toxic gas with a sharp, pungent smell. It is primarily produced by the burning of fossil fuels, especially coal and oil, but can also be emitted by certain household appliances that burn these fuels, like gas stoves and heaters. While sulfur dioxide is more commonly associated with industrial pollution, it can still be found indoors, particularly in poorly ventilated areas where combustion occurs.

SO₂ is dangerous to humans because it can irritate the respiratory system, leading to coughing, wheezing, and shortness of breath. Long-term exposure to sulfur dioxide can worsen conditions like asthma and bronchitis, and in high concentrations, it can cause severe lung damage. Proper ventilation is key to minimizing the risks associated with sulfur dioxide in the home.

Nitrogen dioxide (NO₂) is a reddish-brown gas that is primarily produced by the combustion of fossil fuels, such as in car engines and heating systems. In the home, it is most commonly found from gas stoves, fireplaces, and other appliances that burn gas or oil.

Nitrogen dioxide is harmful to humans because it can irritate the respiratory system, leading to symptoms like coughing, wheezing, and shortness of breath. Prolonged exposure to elevated levels of NO₂ can exacerbate conditions like asthma, bronchitis, and other lung diseases. It can also make the lungs more susceptible to infection and reduce overall lung function, especially in children and people with pre-existing respiratory conditions.

Radon is a colorless, odorless, and radioactive gas that forms naturally from the decay of uranium in soil and rock. It can enter homes through cracks in foundations, walls, or floors, and is often found in basements or lower levels of buildings.

Radon is dangerous to humans because prolonged exposure to high levels of radon can increase the risk of lung cancer. In fact, radon is the second leading cause of lung cancer after smoking. Since it is invisible and undetectable without specialized testing, radon can accumulate in homes without occupants being aware of its presence.

Formaldehyde is a colorless, strong-smelling gas that is commonly used in the production of building materials and household products, such as plywood, particleboard, furniture, carpets, and some insulation. It can also be released from tobacco smoke, wood stoves, and certain household cleaners. In the home, formaldehyde is primarily found in new furniture or construction materials, as well as in products like air fresheners and disinfectants.

Formaldehyde is dangerous to humans because it is a known carcinogen, meaning long-term exposure can increase the risk of cancer, particularly lung cancer. It can also cause respiratory issues, eye irritation, and allergic reactions, especially in sensitive individuals.

Viruses and bacteria can be found in many areas of the home, including high-touch surfaces like doorknobs, light switches, countertops, remote controls, and faucets, as well as in bathrooms, kitchens, and on shared personal items like towels or smartphones.

These microorganisms can spread through direct contact, air, or droplets from coughs and sneezes. They can cause a variety of illnesses, ranging from mild infections like the common cold to more severe diseases like the flu, COVID-19, or foodborne illnesses, especially in vulnerable populations like the elderly or immunocompromised.