Since the advent of COVID-19, and the established link with respiratory virus airborne transmission, indoor air quality has become especially topical. Earlier this year, the Australian Government held a Clean Air Forum at Parliament House. Australia’s Chief Medical Officer, Professor Paul Kelly, announced that he would be setting up a committee to improve the nation’s indoor air quality over the next 12 months. The absence of clear indoor air quality legislation and Government guidelines have come at a cost. For example, data from the UK shows that more than 11,600 people died after catching COVID in NHS hospitals. In Australia one jurisdiction reported that 1 in 9 COVID infections were hospital acquired in 2020. It’s terrible to think that thousands of patients who went into hospital for unrelated illnesses contracted the disease, with fatal consequences. The risk of compromising the health of patients and staff due to transmission of other airborne disease, ingress of contaminants, and the impact on efficiency – both in financial and productivity terms, is significant.
Review of HVAC systems
During the pandemic healthcare Estates and Facilities managers from around the country reviewed their HVAC systems to determine if air exchange rates met basic hospital engineering requirements. However, of course, air exchange rates for fresh air are only part of the picture. Airtightness of the building’s external envelope may influence airflow leakage just as much as the intra-building barriers separating CSSD, operating theatres, and isolation rooms/wards. Air barriers are the starting aspect to consider, and vital to achieve the goal of reducing the prevalence of hospital-acquired infections. The built environment is an essential component of a hospital’s infection control strategy, as this influences airflow, and ingress of contaminants and moisture, and impacts energy consumption.
Internal air flows are a critical aspect for good infection control. The correct flow and control of air from clean to dirty areas is required to prevent hospital-acquired infections. Hospitals are designed to take advantage of positive and negative airflows, in key areas such as the CSSD. The Australian Commission on Safety and Quality in Healthcare mandatory Advisory AS18/07: reprocessing of reusable medical devices in health service organisations requires compliance to AS 4187 for accreditation. Building airtight sterilisation departments is critical to ensure unidirectional airflow. However, building and ward air permeability is rarely validated, which can greatly impact upon the risk of cross-contamination, and increase the risk of hospital-acquired infections.
Unintentional cross-contamination
Unintentional cross-contamination can occur when excessive uncontrolled air leakage arises between clean and dirty areas, and from one patient or ward to the next. HVAC design and operation, exterior wind speed and direction, building stack effect, and building airtightness, all influence airflow and leakage inside a hospital. To protect occupants from unintentional air leakage, air barriers must be designed and tested to ensure that the construction is fit for purpose. Airtightness testing should be considered in a detailed risk analysis of the facility to reduce the risk of cross-contamination and increase wellness outcomes. In addition to internal cross-contamination, air leakage into the building envelope can cause issues related to moisture and contaminant ingress
Issues with mould
Air ingress causes major issues with moisture ingress and condensation, leading to mould in some facilities. Mould is a major problem in many parts of Australia, and can be disruptive to clinical operations, and costly to clean and remediate, as seen recently in Western Australia. In tropical coastal regions, warm wind transports moisture into poorly sealed buildings. Condensation occurs when the humid air encounters cooler surfaces in the conditioned air space and inside the walls. Special attention is required when constructing hospitals in these climates to ensure that moisture is removed from the outside make-up air, that ventilation is designed correctly, and that buildings are built airtight.
Leaky building envelopes are a major factor for pollution ingress into a hospital from bushfires, helicopter exhaust, cooling tower aerosols, and city smog. Nitrogen dioxide has an odour, and is an acidic and highly corrosive gas that can affect our health and environment. A common source in hospital environments is from infiltration of helicopter exhaust emissions when the helipad is in use. In recent years, a major tertiary hospital commissioned the key supply air intakes to temporarily shut down during helicopter idling and take-off/ landing. It was found that shutting down the outside supply air had little effect on adjacent clinical wards to the helipad, due to gaps in the building envelope. During 2019 and 2020, prolonged exposure to smoke from bushfires caused buildings across the country to be evacuated. Upgrading HVAC filters will not prevent smoke ingress via leaks in the building envelope. Hospital air needs to be kept clean, and care needs to be taken not to exacerbate asthma symptoms during bushfire season.
An ever-higher priority for engineers As Australia edges closer to its climate targets of 2030, improving the energy efficiency of hospitals is becoming increasingly important for Australian hospital engineers. Hospitals are among the most energy-intensive buildings, and reducing energy consumption can have a significant impact on reducing greenhouse gas emissions. Improving airtightness has shown that demand for air-conditioning and heating can be reduced by up to 15%, leading to major savings in electricity bills, and meaningful reductions in energy consumption.
To achieve airtight clinical spaces in healthcare buildings, the design should be reviewed to ensure continuity of the air barrier around penetrations, transitions, and interfaces. The construction crew must be aware of the design requirements., and audits should be performed at key stages of the project to ensure compliance. Air leakage should be validated to ensure that design requirements are met which can be implemented in individual clinical rooms, the building façade, and whole building.
In addition to commissioning, airtightness testing should be carried out every five years in critical areas. This recommendation is made as air leakage can increase over time due to structural movement, day-to-day wear and tear, refurbishment, repairs that penetrate the air barrier, and material shrinkage and degradation. Through testing, these issues can be identified and addressed, leading to improved indoor air quality and reduction in energy consumption, lower power bills, and a reduced need to purchase carbon offsets.
Via appropriate design and validation of the air barriers, the airflows in the facility can be better managed to reduce the risk of cross-infection, and the ingress of external contaminants and achieve higher energy efficiency. This will ultimately both result in better patient and staff health outcomes, and lower the costs of operating the facility.
Further reading
Exclusive: 11,600 people caught Covid in hospital and died. The Telegraph. 8 November 2021. https://tinyurl. com/2xmdexys
Streifel A, Geeslin A, Nelson, G. (2006). 231. Airborne Infection Isolation Room Leakage Analysis. 231-231. 10.3320/1.2753382. AIHce Conference 2006.
Veale HJ, Dale K, Ampt F, Kalman T, Kaufman C, Gibson E et al. COVID-19 Hospital-Acquired Infections Among Patients in Victorian Health Services (25 January 2020- 15 November 2020). Final Report. Victorian Department of Health.
Acknowledgment This article, titled ‘Building the fabric for infection control and energy efficiency’, was previously published in the July 2023 edition of Healthcare Facilities, the official journal of the Institute of Healthcare Engineering, Australia. HEJ thanks the IHEA, the author, and the magazine’s publisher, Adbourne Publishing, for allowing its reproduction here.