Issues with Indoor Air Quality. A Health Friendly Air perspective

This blog has been written by John Fallon PhD, senior scientific officer in the microbiology laboratory of airmid healthgroup


In this blog, we discuss issues relating to the quality of indoor air and the impact indoor air pollution can have on human health with Health Friendly Air, a division of airmid healthgroup. Given that the majority of a person’s time is spent indoors, a good standard of indoor air quality is an essential facet in the prevention of infection and disease. Herein, John Fallon PhD touches on topics ranging from potential indoor air contaminants, the diseases they may cause, and methods to ensure a high standard of indoor air quality.    

Issues with Indoor Air Quality. A Health Friendly Air perspective

Fungal and bacterial microorganisms are a ubiquitous element of the flora that an individual is exposed to on a daily basis. At Health Friendly Air (HFA) we have acquired significant experience in addressing the occurrence of these issues in businesses and homes and as a result we are well placed to detect them and subsequently advise on measures that need to be addressed. The following article considers these issues in the context of other indoor environmental factors and how seasonal changes in building maintenance have been shown to affect indoor air quality (IAQ).

The term “Sick Building Syndrome” was initially used to describe “a building in which complaints of ill health are more common than might reasonably be expected”. The manifestation of medical conditions associated with poor indoor air quality have been shown to include eye, ear, nose or throat irritation, wheeze and tightness of the chest, headaches, nose bleeds, skin sensitisation and general lethargy as well as exacerbation of asthmatic conditions. (Finnegan et al., 1984). In addressing IAQ, experience has shown us that the multifaceted nature of the indoor environment results in many variables that may result in conditions that favour the development and concentration of air pollutants. Humans by their nature shed skin, exhale carbon dioxide and are a source of volatile organic compounds as well as being a harbour for pathogens and allergens. These factors, and the need to reduce them, have been shown to play a major influence on the perception of IAQ.

In recent years the need to find a balance between IAQ and sustainable building development has been affected by a greater emphasis on improved energy conservation in new and renovated buildings. These changes are necessary and provide economic benefits over time but are frequently at the expense of the preservation of adequate ventilation resulting in the development of conditions that allow for the proliferation and persistence of advanced microbial colonisation. In turn, changes to optimal physical, thermal and gaseous conditions can seriously hinder the building occupants’ comfort and productivity with reduced concentration, lethargy and a reduction in the perception of IAQ. Many of the materials used in building interiors contain cellulose. Cellulose is a ubiquitous polysaccharide and is the primary constituent of the plant cell wall. Complex sugars such as cellulose can be broken down to simpler carbohydrates that can be easily absorbed. As molds often occur as saprophytes (organisms that acquire nutrients from decaying vegetation including plants),  cellulose is an excellent substrate for fungal growth, with a body of evidence demonstrating its presence in building materials (such as tiles and joinery) favours conditions for fungal growth and proliferation (Karunasena et al., 2001). In nature fungal species often function in the process of decomposition and cycling of nutrients, therefore their visible presence in the indoor environment is of particular concern in the maintenance of the structural integrity of the building. Certain mold genera including Aspergillus, Penicillium, Stachybotrys, Cladosporidium, Mucor and Alternaria as well as species from the phylum Basidiomycota have been heavily implicated in fungal infection and sensitisation reactions acquired in the indoor environment. The ability of these fungi to colonise and grow on the numerous materials and textiles used in modern building construction while being able to withstand significant variation in temperature, moisture and pH represents a significant issue for asthmatics and for some people with underlying medical conditions. Individuals who suffer from asthmatic fungal sensitisation are particularly at risk of developing allergic and asthmatic reactions thus greatly reducing their quality of life. In cases where individuals are immunosuppressed or have existing pulmonary issues such as emphysema, tuberculosis or cystic fibrosis this becomes a greater risk with mortality rates from invasive infections notably high. It follows that the economic impact owing to the cost of healthcare to individuals and the loss of comfort and productivity as a result of indoor mold growth means that there is an acute need to prevent and eliminate fungal colonisation and persistence in the indoor environment.

The natural ventilation of office and industrial buildings generally reduces during winter months due to the need to retain heat in colder weather. As a result, the cumulative effect of increased humidity due to inadequate ventilation coupled with the seasonal increase in airborne mold means that the incidence of IAQ issues increases during the autumn and winter. Modern office buildings rely in many cases upon an effective HVAC (heating, ventilation and air conditioning) system for the purpose of supplying adequate ventilation and correct thermal regulation depending on the time of the year and the associated climate. While recognising the need to maintain thermal comfort, issues relating to air recirculation and temperature adjustment can result in suboptimal conditions for employee productivity. For example low relative humidity (<40%) can lead to drying of the mucous membranes, which can cause discomfort. Increased carbon dioxide from the recirculation of office air has been shown to result in a dimunition of occupant concentration over time. Additionally HVAC systems have been shown to be an ideal area for the development of microbial proliferation when not properly maintained. There is a high level of regard given to the risks associated with Legionella contamination in HVAC units, which is entirely merited given its significance as a pathogen in Legionnaires’ disease and Pontiac fever. It must be stressed however that incorrect maintenance of HVAC units and associated ductwork has also been shown to result in higher levels of other pathogenic bacteria and fungal microorganisms. Given the recirculation of air during operation, a contaminated HVAC unit or associated ductwork can have a marked influence on IAQ as we have observed a direct correlation between duct contamination and airborne microbial counts.

Irish legislation states that employers have a general duty to employees to ensure the safety, health and welfare at work of his or her employees (Part 2 Chapter 1 of the Safety, Health and Welfare at Work Act, 2005). In addition section 2, schedule 2 of the Safety, Health and Welfare at Work (General Application) Regulations 2007 (S.I. No. 299 of 2007) states that “steps should be taken to ensure that there is sufficient fresh air in enclosed places of work, having regard to the working methods used and the physical demands placed on the employees”. It is therefore evident that an indoor air quality audit should play a key role in the protection of employee health. As well as the potential threat of litigation, there is the potential financial stress implied by days lost to employee sick days. As a result it is evident that correct monitoring of air through a regular review of airborne microbiological content as well as physical and chemical parameters that are most likely to affect occupant health should be an integral part of employer health and safety statements.

With this in mind, the Health Friendly Air division of airmid healthgroup was formed in 2009 to enable clients to identify and address current and potential IAQ problems. Health Friendly Air combines expertise from occupational hygienists, scientists and medical professionals to offer a comprehensive service that is valued by employers, employees and homeowners. Our ability to design the most appropriate quality driven tests and procedures for indoor spaces as diverse as homes and office spaces is unmatched in our field. Furthermore, our commitment to providing a comprehensive service means that the homeowners, health & safety officers and office managers can have the peace of mind that they are being equipped with the best knowledge of the status of their IAQ.


Finnegan, M.J., Pickering, C.A.C. and P.S. Burge, (1984). The sick building syndrome: prevalence studies. British Medical Journal, 289: 1573 – 1575.

Karunasena, E., Markham, N., Brasel, T., Cooley, J.D. and D.C Straus, (2001). Evaluation of fungal growth on cellulose-containing and inorganic ceiling tile. Mycopathologia 150: 91 – 95.

About airmid

airmid helps their clients across a number of sectors improve, add value and differentiate their customer offerings through a focus on bio-medical data, health impact claims and optimising indoor air quality. We have a uniquely integrated facility, which combines standard microbiology testing, molecular biology and state-of-the-art air sampling with a highly developed climate controlled walk-in environmental test chamber. This gives us a world-class aerobiology research facility that allows us to follow airborne pathogens such as nominated viruses, bacteria, molds or other ultra-fine particles. As a world leading bio-medical research facility our clients describe us as a specialised extension of their research capabilities. We capture, store and manage data and most importantly convert it into tangible market value.

Contact Fraser Hodgson if you have any questions on the issues raised in this article and to learn how we can add value to your company:


About John Fallon PhD

Senior Scientific Officer – Microbiology Testing Laboratory


John graduated from the National University of Ireland Maynooth (NUIM) with a BSc in Biological Sciences. Following completion of his undergraduate studies, John remained at NUIM to complete a PhD in the medical mycology unit examining the disease causing potential of environmental isolates of Aspergillus fumigatus in vertebrate and invertebrate immune systems. John has significant experience in the field of mold culture and phenotypic analysis as well as having published data concerning the detrimental effects of mycotoxins produced by A. fumigatus on the function of immune cells.




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