Indoor air quality is closely linked to health.
Many of us spend most of our time indoors, so it is important that air circulating in enclosed spaces is of a high quality.
Dangers lurk in unexpected places. Innocent objects such as furniture or cleaning products can emit what are known as "volatile organic compounds".
These compounds can be harmful to health and increase the risk of chronic respiratory disease.
They can also be emitted from building materials and electronic equipment.
But companies that take on the Greenguard certification will be taking a step towards creating a healthier indoor environment.
This certification ensures that the products and materials the holder produces have met rigorous, comprehensive standards.
Attaining certification means manufacturers have made a commitment to consistently produce non-toxic low-emitting products.
Firms applying for the certification will need to submit their products for emissions testing.
During this process, items are tested for pollutants such as formaldehyde, ozone and particles that could be breathed in under circumstances that mimic typical indoor environments.