Indoor air quality (shortened as IAQ) refers to the general air quality within buildings and structures, specifically in locations used by people. IAQ is particularly important to a building's occupants, as it has direct consequences on their comfort and health. Air pollutants, coming from a series of sources, can cause serious health problems to occupants, particularly after long periods of exposure. In order to avoid the effects of air pollutants, it is critical to understand what they are and how they affect occupants. Also, we need to determine the pollutants' common pathways (cracks, fissures, leakages or poor ventilation system design) and how we can avoid these situations (filtering, redesign or relocation), while ensuring a comfortable living environment for occupants.
Identifying the Problem
Indoor air quality problems can be caused by numerous technical or design errors, biological and chemical hazards, as well as everyday human activities. Generally, indoor air quality problems are present when four separate elements are involved:
Source – the contamination source can be either outdoor (such as roadways or polluted water) or indoor (such as mechanical systems in the building)
HVAC system – the HVAC system is unable to control the air quality and ensure thermal comfort for occupants
Pathways – they move the contaminant between the source and the occupant
Occupants – they are the people who live, work or study in the building
The role of each of these elements differs depending on the type of contamination, but it is crucial to understand them in order to prevent, assess and resolve indoor air quality problems. Let's see a breakdown of the main types of pollutants identified by HVAC experts:
Second-hand smoke – this refers to tobacco smoke which affects people, other than the active smoker. Although many buildings have strict rules when it comes to indoor smoking, secondhand smoke remains one of the leading indoor air pollutants. Tobacco smoke contains a gaseous and a particulate phase, both having high levels of carbon monoxide, nicotine, ammonia, formaldehyde, hydrogen cyanide, arsenic and DDT. Although modern HVAC systems are equipped to stop the spread of second-hand smoke, strict smoke-free rules must be implemented in every commercial building.
Radon – radon is a radioactive atomic gas which is responsible for thousands of deaths caused by lung cancer each year. This invisible, odorless gas is formed during the natural decay of radium, which is a component of construction materials. Many US jurisdiction require regular radon testing for homes and office buildings, but the risks are still high, particularly in well insulated buildings (certain thermal insulation materials have radium in their composition). Radon mitigation includes the sealing of concrete slabs, basements, drainage system and increasing the ventilation of rooms (air change per hour).
Molds and other biological sources – molds can cause serious indoor air quality problems, particularly if there are ventilation issues in the building which promote the accumulation of moisture. Mold mildew release allergenic spores in the air, which can linger for weeks after the contamination. To avoid mold growth, humidity levels must always be below 50 percent. Also, the roof, the drainage pipes and other possible leaking spots should be checked at all times by qualified personnel. Other biological contamination sources, such as animal dander, droppings and urine, as well as plant pollen should be controlled by the HVAC system and special filters, but also through proper hygiene protocols.
Legionella – the Legionella is a genus of bacteria which causes Legionnaire's disease, a common indoor air quality problem in commercial buildings around the world. Legionella grows in humid locations around buildings and it lingers on wet objects, typically cooling towers, showerheads, taps and AC unit components. For instance, indoor fountains and gardens were found to be breeding grounds for this bacteria. Legionnaire's disease goes unnoticed in many patients, as the infection can linger for years before any symptoms occur. In order to avoid Legionella contamination, periodic testing of water sources, filter changes and correct maintenance of HVAC systems are essential.
In order to live, work and study comfortably, we need a comfortable environment. Thermal comfort, for instance, in many areas of the country, is made possible by the use of complex HVAC systems. Although these systems are designed to create a safe environment, they can be infected by contaminants. Fortunately, most pollutants are not dangerous and can easily be controlled. Moreover, good hygiene protocols, adequate maintenance of HVAC systems can help avoid many of the indoor air quality problems that can affect a building's occupants.