Indoor air pollutants come from many sources, including:
building materials (including fittings and flooring)
furniture and furnishings
consumer products, including household and personal care products
activities such as cooking and smoking
biological sources, including mould, house dust mites, bacteria, pests and pet dander.
Exposure to indoor air pollutants including, for example, nitrogen dioxide, carbon monoxide, particulates, biological agents and volatile organic compounds (VOCs), is widespread and can cause respiratory and other conditions, and premature death in some people. Asthma is a common respiratory condition, with over 5 million people receiving treatment for it in the UK. Indoor air pollutants such as dust mite allergens, nitrogen dioxide and particulate matter are small enough to get into the lungs, making the airways inflamed and swollen. This can exacerbate asthma symptoms and trigger asthma attacks.
It is best practice to reduce pollutant sources and reduce emissions as much as possible, especially for those who are more vulnerable to health problems caused by poor indoor air quality. This includes children and people with respiratory and cardiovascular conditions (Committee on the Medical Effects of Air Pollutants guidance on the health effects of air pollutants).
Usually the most effective way to deal with indoor pollutants is to either remove the source or reduce emissions from it. If these are not possible, the pollutant can be diluted by ventilation (for example, opening windows) to reduce exposure. But outdoor pollutants also enter through windows or gaps in the structure and are a significant contributor to indoor air quality, particularly in deprived areas (see the government's clean air strategy 2019). NICE has also produced a guideline on outdoor air pollution.
This guideline covers the whole population. But special consideration has been given to those at increased risk of exposure to or adverse effects from poor indoor air quality.