How INDOOR AIR COMFORT
Find out more about the ways we identify, react to and cope with odors and stuffiness...
THE PHYSIOLOGICAL ASPECT
The human nose is a very sophisticated organ. Testing instruments are still being developed to try to replicate the way it evaluates air quality – some successful, others less so. This is partly due to incomplete understanding of the way the brain processes information, but also to the high sensitivity of the human nose.
We inhale and exhale an average of 12,000 litres of air per day. Our ability to assess the quality of this air involves our sense of smell, and our ability to sense irritants.
Within each human nostril, there are two types of nerve fibers – the olfactory tissue and the trigeminal nerve – with 30 million receptor cells across a surface area measuring just 5cm2. While the olfactory tissue senses smell, the trigeminal nerve endings sense irritant aspects of chemicals in the air. When they’re stimulated by pollutants, both nerve endings send information to the brain for interpretation, influencing both conscious perception (of bad smells, for example), but also unconscious mood and emotions.
Building materials, furniture, human activities or bioeffluents from people and pets may all cause odors. Odors are generally generated by volatile molecules or a combination of different ones in such a concentration (Volatile Organic Compounds – or VOCs) that they can be detected by the human nose.
Although there’s no evidence to prove that unpleasant odors are linked to adverse health effects, scientific research shows that they can cause mental distraction and may have a negative impact on mood and stress levels.
We can all identify with the sensation of stuffiness in an indoor environment. And it’s often characterised by a headache and feeling of fatigue. This results from the overall pollution load. Many different pollutants – which include odorous VOCs, products of incomplete combustion and bioeffluents – are present in indoor air at very low concentrations. Combined, however, they adversely affect wellbeing.
THE PHYSICAL ASPECT
Over the last couple of centuries, industries have developed, mechanical services have been introduced into buildings, synthetic materials have been invented, motorised transport has become standard and human activity has densified around the world’s growing cities. The quality of air – both outdoors and indoors – has changed accordingly.
The different indoor pollutants can be classified into two main categories:
Physico-chemical pollutants – gases and vapours (inorganic and organic) and particulate matter, such as carbon dioxide, carbon monoxide, VOCs, particles, fi bres, ozone, etc.
Biological pollutants – microbiological (dust) particles floating in the air that originate from viruses, bacteria, mold, mites, insects, birds, mammals and pollen. These include allergens, endotoxins and mold (which can be both allergenic and toxic).
Products present in a building can emit substances (particles and/or gases) that originate from the product itself (primary emissions), that are caused by coming into contact with other products, or that arise during the in-use phase of the product itself (secondary emissions).
Human exposure to indoor air pollutants is influenced by factors such as the ventilation rate within a building, air velocity, temperature, relative humidity, the activities taking place, and the frequency and duration of exposure.
Eliminating risks at source or through good ventilation will help ensure the quality of the indoor air that we spend most of our lifetime breathing.