Indoor Air Quality (IAQ): how to improve your air quality through ventilation, humidity levels, temperature, filtration, and purification
Jon FleetBusiness Development Manager
The air we breathe affects every part of our body, from our lungs to our heart and brain and with the average person now spending at least 90% of their time indoors the quality of our indoor air is of increasing concern. The concentrations of some indoor pollutants are often 2 to 5 times higher than typical outdoor levels and in some cases, these concentrations can exceed 100 times that of outdoor levels of the same pollutants
Increasing building airtightness and a lack of adequate ventilation, often through misguided efforts to ensure energy efficiency have resulted in indoor environments that are stale, humid and contaminated.
How to improve air quality through adequate ventilation
As we breathe in the air oxygen is transferred to blood vessels within our lung sacs in exchange for carbon dioxide (CO2) which is breathed out. This slowly increases the level of CO2 in an unventilated room which will typically see levels of CO2 rising to around 800 ppm. At levels higher than this we will experience tiredness and loss of concentration so it is essential that this is monitored and an adequate supply of fresh air is maintained.
Whilst background ventilation devices and opening windows may be the simplest method of increasing ventilation we need to find a balance between ventilation and thermal comfort, especially in the winter months. An efficient method is to install a Mechanical Ventilation Heat Recovery (MVHR) system. This air-to-air heat exchanger recovers heat from the extracted air that is usually wasted and transfers it to the incoming air, recovering up to 90% of the ‘free heating’. In addition, this system may be controlled by humidity and carbon dioxide sensors to increase and decrease the ventilation rate automatically during times of peak use and even to ramp down or switch off completely during times of inactivity.
Optimum temperature and a comfortable indoor environment
Temperature control is critical to maintaining a comfortable indoor environment and the optimum thermal comfort is usually found between 20 – 22 °C. If the zone is being heated the warmer lighter air rises and if it is being cooled the colder heavier air will sink.
During the ventilation of the occupied space, two zones are formed, the transition zone and the comfort zone. The comfort zone is the air volume where people live and is generally defined as the area from floor level to 1.7m high and up to a distance of 0.3m from the walls. In this zone, the absence of extreme air movements and temperature differences is the main design goal for good air distribution. The supply of air into the transition zone mixes with the surrounding air and the air velocity gradually decreases. For the resident’s comfort, this transition zone must be outside of the comfort zone.
An important element of a residential building ventilation system is the air distribution grilles and diffusers which are installed in the ceiling, walls and floors. Their role is to distribute the air provided by the ventilation system in a way that does not impact the comfort of the people living in the living space.
The correct relative humidity levels for a healthy indoor environment
The correct humidity level plays an important part in a healthy indoor environment. It is a measure of the actual water vapour present as a percentage (%RH) of the saturation level. It is, therefore, dependent on temperature as warmer air has a greater capacity to carry water vapour.
High humidity is often a result of poor heating and ventilation giving rise to mould, bacteria, dust mites, etc resulting in respiratory problems and infections. Low humidity is mainly caused by excessive use of air conditioning or heating, particularly during colder weather. It allows pathogens in aerosol form to survive longer and aggravates allergies, eczema, dry eyes, etc.
A range of relative humidity between 40-60% reduces the risk of virus infection and is the optimum humidity level that we find comfortable. Humidity sensors and de-humidifiers and humidifiers are simple solutions to creating an environment that is healthy and pleasant to live in.
Building Regulations stipulate minimum ventilation requirements for each type of room to ensure that excessive moisture is removed and air quality requirements are met.
Improving indoor air quality with particle filtration
Dust, pollen and microbial organisms are natural particles whilst soot and smoke are air pollutants from car exhaust and power plants. These are held in the air as aerosols, which are the suspension of solid and liquid particles typically defined by size. These particles make their way inside through windows, doors, gaps in the structure and by mechanical ventilation such as ducted ventilation or air conditioning systems. Particles are also generated inside through cooking, wood stoves and candles and include biological particles such as bacteria, mites and fine dust.
Most particles are linked to asthma and other lung conditions where exposure over time will cause irreversible damage and weaken the body’s immunity to diseases. The smaller particles have the greatest impact on our health.
Fibre air filtration can be described as the first line of defence against airborne contaminants. Climate control systems contain filters, ranging from basic filters which remove sand, hair and other coarse particles to specialised High-Efficiency Particulate Air (HEPA) filters capable of trapping particulate matter as small as 0.3 microns.
When you should install a carbon filter
While fibre filters may be effective at trapping a large proportion of particles, they do not remove odours, chemicals or gases. Pollutant gases such as Nitrogen oxide (NOx) created by road transport, are typically high adjacent to busy roadways and will make their way inside the home. They are harmful to the lining of the lungs and may reduce immunity to other illnesses. Modern furniture finishes, air fresheners, carpet and oven cleaners may contain chemicals called Volatile Organic Compounds (VOCs). When these are released into the air they evaporate readily at room temperature, are toxic and cause symptoms such as eye and skin irritation, and allergic reactions. They also have long-term health effects such as chronic respiratory problems, loss of coordination, damage to the kidneys, liver and central nervous system, and cancer.
Activated carbon filters are manufactured from small pieces of carbon, typically in granular or powdered block form, that has been treated to be extremely porous and is very effective at capturing pollutants such as chemical emissions including Volatile Organic Compounds (VOCs), smog, ozone, fumes from cooking tobacco smoke.
Will air purification improve indoor air quality?
Air Purification for residential homes is available through a variety of standalone devices ranging from devices that provide filtration only to those that filter, humidity and purify. These devices are generally low performance and designed to provide limited protection within a small area of the home. Built-in air purification systems integrated within the HVAC system are the best solution to give total cover and demand control at the correct locations.
Ultraviolet Light has been used for a long time to purify water, surfaces and air and has been proven to be a reliable and safe method. Ultraviolet light has a shorter wavelength than visible light and a much higher energy level. When this energy is absorbed by a microorganism such as bacteria, viruses, and mould it damages the DNA of the cell which triggers a self-destruct mechanism rendering it harmless.
Bipolar ionization air purifiers (also called needlepoint bi-polar ionization) are a technology that can be used in ducted ventilation systems to generate positively and negatively charged ions. They magnetically attract airborne particles such as pollen and dust, until the newly-formed particle is too heavy to remain in the air or is large enough to be removed by a filter.
Hydrogen peroxide air purifiers, are also designed for ducted ventilation systems and use an electrical discharge current to produce Hydrogen Peroxide (H₂O₂) from the Oxygen O₂ and Water humidity H₂O in the air, which is effective for the elimination of bacteria, viruses and mould. They have a long-lasting effect and proactivity treats every space within the ventilated zone.
Is maintenance important to maintain my Indoor Air Quality?
Climate control systems must be maintained. Scheduling regular maintenance visits and following through on minor repairs is essential. One of the key benefits of maintaining an HVAC system is Healthy Indoor Air. A properly maintained HVAC unit will not only keep the indoor climate at the correct temperature but will prevent problems with air quality. Clean filters and coils ensure an indoor air quality free of pathogens and particles. An unmaintained HVAC unit is a breeding ground for dirt, mould and bacteria, all of which can cause or worsen respiratory problems for those living or working within the building.