04 April 2016

Indoor Air Quality (IAQ) in Hospital Environments

Gold Coast Private Hospital

Considering the vast number of Hospitals and Medical Centres within Australia, one would expect that the solutions for Indoor Air Quality (IAQ) would be routine. However, while the aims of good IAQ are easy to express – the diverse range of sites and environments, create a remarkably complex situation.

This article seeks to set out the broad aims and parameters in IAQ, and explore the sources of major threats to maintaining good IAQ within Hospital environments.

Measurable Factors Affecting IAQ in Hospital Environments


Although room pressurisation and particle filtration gain a great deal of attention, humidity is a very significant factor in the air quality equation. Humidity or dampness in building materials, when combined with elevated temperature, serves to encourage the growth of mould and fungi.

Although many of these mould or fungi organisms are fairly benign – there are notable exceptions that have a high profile as hideously dangerous, particularly when patients are immune compromised. Compounding these concerning factors, moulds and fungi are known to emit mycotoxins into the air –further aggravating respiratory issues.

Routine, scheduled microbiological testing should be completed to assure that undesirable pathogens such as mould or fungi are not at excessive levels within your facilities. Regular inspections of building materials and surfaces should assist in the detection of leaks and other potential vulnerabilities. Similarly, finely controlled HVAC systems and automated building management systems (BMS) that continuously monitor the key factors that modulate humidity are useful tools to deal with excess humidity and its undesirable impacts.

AireCell_HEPA_FilterIn-duct gasket seal HEPA filter 

A significant hidden threat to IAQ is the contribution of the HVAC and filtered air delivery systems to various locations in the hospital. While HEPA filters will entrap the various moulds and fungi that reach them, over time live organisms can penetrate (grow through) even the best quality media. So attention to duct cleanliness and the “up-stream” control of temperature and humidity is an important factor in overall success.


Overseas, germicidal UV has gained some measure of acceptance in recent years. UV irradiation of the air stream and devices in the airflow path may reduce microbiological load. If these systems are implemented correctly, very persuasive data exists on the success of these techniques. Important considerations for these systems include the selection of correct lamps, array of light intensity, set maintenance routines and adequate interlocks to keep workers safe from random UV exposure.

TechnicleanSimilar to effective HEPA systems, these germicidal UV solutions are not “free”, but can contribute in a significant way to the destruction of unwanted microbiological activity, and are worthy of consideration as a tool in the overall design of a successful system.

In-duct UV-C light technology filtration system

A variety of disinfection services and protocols exist in this field, to control and remove biological contaminants. It is outside the scope of this discussion to elaborate on these here.



Temperature is another significant factor in the air quality equation. Patient comfort as well as conventional attitudes towards comfortable user temperatures will be the predominant driver for room settings. As previously mentioned, humidity in building materials, when combined with elevated temperature serves to encourage the growth of mould and fungi. Less obvious threats to IAQ are the thermal profiles in the HVAC system that may induce enhanced microbiological growth or condensation effects that may create leaks, puddles or surface condensation. Simple observation of facility surfaces and temperature probes monitored through a BMS and are routine tools in this area.

Chemicals and Outgassing

This topic covers a vast range of potential chemical hazards and threats to IAQ within Hospital environments. While several chemicals are popularised as harmful (such as outgassing of formaldehyde from building materials and the like), the linkage between various cleaning chemicals, surface outgassing and environmental gases drawn into a building are still a topic of study and controversy. Our only pragmatic response is to control inlet air as much as possible to “clean” source areas, or add chemical media filters (such as activated carbon) capable of extracting harmful chemicals (such as diesel emissions) from the inlet air. Adequate air changes and rational control of room pressurization flows enhances these basic steps.


Mini-pleat activated carbon media filter

If an air quality issue is thought to exist, containment of the source is the first remediation that should be attempted, then if possible, review if there are less objectionable materials that can be substituted. If the chemical is unknown or of unclear origin, a commercial test lab that is experienced in chemical air quality testing can be engaged to validly capture air samples, and then perform chemical analysis (generally GCMS) to identify and quantify various contaminants, then judge their potential for injury. This is not an inexpensive process, or swift process, as the valid collection of samples is a very demanding process, and the downstream analytical instruments are very expensive to own and run.

Room Pressurisation and Airflow

AS1668.2, and a number of State Health Guidelines determine the correct airflows, room air changes, and level of room-to-room pressurization. It is simple to find this information – and less easy to conform to these values in practice.

For example, standards for Operating Rooms as per AS1668.2 include minimum air change rates calculated to achieve 20 changes per hour, minimum outdoor airflow rates calculated at 20 L/s per person at an occupancy of 5 m2 per person, and air pressure maintained at a higher rate than that in adjacent enclosures other than sterile store and set-up rooms.

The temptation to “just-comply” with the minimum values of regulations and guidelines in the “specification” and “building” stage of a job, is inescapably driven forcefully to decrease building costs. If one just operates at the minimum values, any disruption, wear or contamination of filters and ducts will have a dramatic impact on the robustness of the entire air handling system and control protocols, ultimately affecting the air quality that patients experience. It is important to note that in the life of a Hospital building, and in view of achieving the best possible outcomes for patients – cost cutting in this area is antithetic to the building’s real goal and purpose.

NATA certified HEPA integrity testing

NATA certified HEPA integrity testing

At a finer level of design, the best possible selection of air delivery devices (such as HEPA housings and the like), can enhance the long-term performance and delivery of good IAQ. More subtle – the location and existence of adequate duct service ports to allow NATA testing and certification of HEPA performance is important, to reduce test costs and enhance the validity of the completed tests.



Perhaps the most obvious solution to overall IAQ is the most “hidden”. Particulate material can be removed almost totally by a sequence of carefully chosen filters. HEPA and ULPA filters, run at the correct air flow rates, will remove more than 99.97% of particles at 0.3um. This “value”, 0.3um is selected as the test point because particles above and below this size – are generally easier to capture – so these are the most “elusive” particles – hence the value of rating filters for efficiency at this size.

Focus 3000 CFD ModellingFocus UCV unit with HEPA filters showing CFD modelling of contaminant free air supply over an operating theatre table.

These very effective and valuable HEPA filters need to be protected by a series of sacrificial (cheaper) filters that have a lower capture rate of efficiency – but remove most of the common – larger particles from the air stream. Various ratings are applied to these filters, G4, F8 etc., that all reflect various standardised test methods that are used to rate filter media.

In general, there are two sets of filters before a HEPA in the HVAC air stream. For an operating theatre, typical pre-filter selection would comprise a 100mm deep G4 rated pleated filter and a F8 rated bag filter held within a combination frame. These pre-filters are sequentially arranged to trap course particles, then finer particles to leave a fairly clean air stream for the HEPA filter to collect the very fine particles. If these “sacrificial” filters are not changed often enough, or are compromised by bypass (leakage due to inferior filters or inadequate housings), they will pollute the HEPA filter – reducing its working life from 3-4 years to at worst, days.

Airepure F3 Frame G4 Airepleat F8 Airepak6P

100mm deep G4 rated pleated filter and F8 rated bag filter held in combination frame.

There are a variety of particle counting processes and services; NATA certification is the most rigorous of these. Care should be taken to assure that the devices used for these services are calibrated and appropriate to the task – and the users, fully familiar with the devices proper operation.


Indoor Air Quality is a critical parameter in patient outcomes for hospitals and medical centres. This article has highlighted a number of the factors that contribute to IAQ, and some control aspects and decisions that can lead to better outcomes. An exemplary level of IAQ for health facilities is an achievable goal – it just takes quality design and implementation and rigorous attention to detail in the operation and maintenance of the facility.

Written by Shannon Roger (B.Ed) and Dr Allan Heckenberg (PhD) for Airepure Australia 2016.  This article was published in The Australian Hospital Engineer Journal, Vol 39, No 1, March 2016.

Airepure Australia offer a range of products, services and consulting expertise that can assist you with your compliance to ACHS, DHS VIC Guidelines (and equivalent for QLD, WA and NSW), ISO/IEC 17025:2005 Requirements, AS/NZS 2243.3:2010 and AS/NZS 2243.8:2014. Airepure is a leading national air filtration company providing unique, powerful and integrated air filtration solutions, ranging from basic HVAC filtration and odour control right through to high end HEPA/ULPA filtration and airborne containment technologies. Airepure recommends ELTA and Fantech Fans.


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