The quest for clean air dates back to Hippocrates (c. 460 — 377 BC), often considered the ‘Father of Medicine’. He emphasised the effects of environmental factors, including air quality, on human health. He linked the characteristics of the air in a region to the prevalence of certain diseases. He believed that understanding the winds, seasons, and the quality of air and water was crucial for a physician to understand the health of a community. Throughout history, philosophers were influenced by the Miasma Theory, which posited that diseases were caused by ‘miasma’ — bad air from decaying organic matter. While there is no demand for ‘clean’ air in the modern sense, it highlights the perceived danger of ‘foul’ air, and implicitly suggests the need to avoid such conditions to prevent illness.
Later thinkers, such as the jurist, Sir Edward Coke, in the early 1500s, argued that ‘lights and sweet air were as necessary as pure and wholesome water’. In his letter to King Charles II in 1661, John Evelyn expressed grave concerns about the poor air quality in London, attributing it to the burning of coal, and highlighting its detrimental effects on public health — including coughs, low birth rates, and high mortality. Later, in the 19th century, public health reformers like John H. Griscom in New York actively campaigned for improved living conditions, including better ventilation and cleaner environments, to improve public health. While not strictly philosophers in the traditional sense, their work was driven by a philosophical concern for the well-being of the population.
The early hospital design
Most hospitals’ early purpose was to house — not cure — the sick, in tightly packed rows of beds in dark open wards. Florence Nightingale, known as the ‘Lady with the Lamp’, decided to fundamentally change healthcare forever with her insights into patient recovery and environmental factors like air quality and ventilation. During the Crimean War, she observed the dire sanitary conditions in military hospitals, and identified the link between the environment and patient mortality. Her detailed data collection revealed that preventable diseases were the primary killers, prompting her to implement vital reforms in hospital management.
Nightingale emphasised the importance of fresh air and proper ventilation, advocating open windows and cleanliness as key infection control measures. Her innovative statistical analysis, including famous Coxcomb charts, provided compelling evidence for the effectiveness of her sanitary reforms, convincing sceptical medical authorities. Her influence reached beyond her wartime efforts, shaping hospital design and public health practices. Nightingale’s writings, particularly Notes on Nursing, became essential for nursing education, highlighting the significance of observation and hygiene. By fostering a culture of continuous improvement and empowering nurses to participate actively in patient care, she elevated the profession to one requiring specialised knowledge.
The later acceptance of germ theory
Florence Nightingale’s focus on air quality also anticipated the later acceptance of germ theory, laying the groundwork for understanding airborne pathogens in disease transmission. In summary, her leadership and commitment to evidence-based care transformed nursing and modern healthcare, establishing her as a pioneer in the field.
In the early 1900s, hospitals shifted gears. They started focusing on curing patients and utilising technologies such as X-rays and cardiographs, which undoubtedly revolutionised patient care and saved the lives of millions. However, keeping the machines needed for treatment near patients represented a significant challenge for the staff, and fundamentally changed how designers approached hospital layouts.
Today, staying overnight in a hospital could mean experiencing a shared room poorly lit by flickering fluorescent light with no windows. Furthermore, the persistent odour might keep the patient up all night if the cacophony of beeping from various old machines does not. Likewise, research has correlated fluctuating temperatures and poor IAQ to ‘Hospital-related illness and Infection’, ‘cross-contamination’, and ‘sick building syndrome’, which can actually deteriorate patients’ health conditions.1-3 So, today, raising the bar of air quality through multi-stage filtration and energy-efficient HVAC systems that are responsive and adaptive constitutes an innovative way toward a modern and sustainable hospital environment.
Understanding the importance of IAQ in healthcare facilities
IAQ in healthcare facilities is critical to patient safety, infection control, and overall health outcomes. Hospitals, clinics, and other healthcare environments, must maintain exceptionally high air quality standards due to patients’ vulnerability, the presence of airborne pathogens, and the necessity of a sterile environment for medical procedures. Poor IAQ can exacerbate respiratory conditions, contribute to hospital-acquired infections (HAIs), and negatively impact the wellbeing of healthcare workers and visitors. Research has emphasised the critical role of indoor air quality in hospitals for the health and safety of staff, patients, and visitors. It highlights the potential health risks and cognitive decline that can arise from poor IAQ.4,5 Additionally, studies have explored the complexities of indoor environmental quality (IEQ) in healthcare facilities, stressing the urgent need for more research to develop healthier and more comfortable environments for all occupants, not just patients.6-8
Maintaining superior IAQ in healthcare settings
Hygienic HVAC (heating, ventilation, and air-conditioning) and filtration systems are central to maintaining superior IAQ in healthcare settings. These systems help control airborne contaminants, regulate temperature and humidity, and ensure the appropriate and efficient indoor circulation of clean and fresh air. An inadequately designed or poorly maintained HVAC system can compromise patient health and safety, increase energy consumption, and elevate operational costs. IAQ in healthcare environments is a determining factor in disease prevention and patient recovery. The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) emphasise the need for stringent air quality measures to mitigate airborne disease transmission, particularly in high-risk areas such as operating rooms, intensive care units, and isolation wards.
Patients in healthcare settings are often immunocompromised, making them more susceptible to airborne infections. Contaminated air can introduce bacteria, viruses, mould spores, and volatile organic compounds (VOCs) into the respiratory system, exacerbating asthma, chronic obstructive pulmonary disease, and pneumonia. Inadequate IAQ has also been linked to the spread of airborne diseases like tuberculosis, COVID-19, and influenza. Furthermore, studies have shown that improved IAQ contributes to faster recovery times, reduced readmission rates, and overall better patient outcomes. Proper air filtration and ventilation in patient rooms and surgical suites can significantly reduce infection risks.9,10
Healthcare professionals are exposed to poor IAQ in hospitals, leading to occupational illnesses like respiratory infections and fatigue, impacting their performance and increasing absenteeism. The high volume of hospital visitors raises the risk of airborne pathogen transmission, complicating IAQ management. Despite efforts to improve IAQ through advanced filtration systems, uncontrolled contamination from staff and visitors remains a challenge. Additionally, environmental factors like sandstorms and wildfires can hinder air filter performance. At the same time, excessive use of cleaning agents containing volatile organic compounds further complicates achieving optimal IAQ, and requires extensive employment of chemical filters.
The question remains: When would a particle become a pollutant, and at what concentration? When should our HVAC and filtration systems respond to the presence of particles and bioaerosol, and at which stage? More critical than infection control is infection prevention, and that requires a well-maintained HVAC system to ensure that contaminants are efficiently filtered, reducing the risk of pathogen spread among patients, staff, and visitors, in the first place.
The road ahead
Ensuring compliance requires continuous monitoring, regular HVAC maintenance, and staff training on IAQ best practices for optimising healthcare HVAC systems. These practices include, but are not limited to:
1 Adhere to a regular HVAC maintenance and filter replacement programme, where routine inspections and data-driven filter replacement are scheduled to ensure optimal system performance and IAQ outcomes.
2 Employ advanced filtration technologies, where chemical filters in an air purification system capable of disinfecting the air for bioaerosols are critically important.
3 Design for zoning and ventilation control where proper pressure relations between various critical/non-critical spaces are maintained by the HVAC system, reducing contamination risks.
4 Implement smart HVAC solutions where system automation can respond to any variations in IAQ through data-driven decisions enabled by air quality sensors, aiming to optimise air quality management and reduce manual monitoring efforts.
5 Provide staff training on IAQ, proper HVAC operation, and best practices, to reduce pollutant transmissions. Training endeavours should also include orienting patients during admission about the essence of infection control protocols that hospitals implement to manage air quality assiduously.
Addressing the imperative steps
Addressing the imperative steps toward enhancing IAQ is crucial, especially in the light of the ongoing challenges that facility management encounters in managing engineering-related air quality issues. A significant concern lies with many hospitals and healthcare facilities, which often operate with ageing infrastructures. These outdated systems, and specifically their heating, ventilation, and air-conditioning components, regularly fall short of meeting contemporary IAQ standards, raising profound implications for the wellbeing of patients and healthcare personnel.
Retrofitting these antiquated HVAC systems is not only complex, but also expensive. Upgrading to advanced filtration solutions — integrating state-of-the-art filter media and sophisticated IAQ monitoring technologies — requires significant technical expertise and financial investment. Unfortunately, many stakeholders view these necessary enhancements as costs rather than critical investments in health, safety, and operational efficiency, which can hinder essential upgrades and ongoing system maintenance.
Furthermore, conventional HVAC systems often struggle to provide the thermal comfort required while adapting to the ebb and flow of human occupancy and unpredictable changes in air quality. With HVAC systems running continuously — 24 hours a day, seven days a week — these facilities experience considerable energy consumption. This reality highlights the pressing need for energy-efficient solutions that effectively balance operational efficiency with the imperative of maintaining superior IAQ.
The concepts of energy recovery ventilation for outdoor air admitted in large capacities — often in healthcare facilities — and demand-controlled ventilation (DCV) to serve highly variant occupied patient and non-patient spaces present promising ways to improve energy efficiency while maintaining air quality via upgraded advanced filtration systems. However, there are challenges to consider. The limited spaces where these advanced filtration and energy efficiency systems need to be installed, and the system/control sophistication associated with retrofitting existing HVAC systems with systems like demand-controlled ventilation, can limit options for achieving the optimal intersection point of improved energy efficiency with enhanced filtration efficiency. A design-focused approach indicates that many filtration challenges arise from the common ‘one-size-fits-all’ method. These issues can be addressed by integrating filtration early in the HVAC design process, ensuring balanced ventilation, energy use, and maintenance efficiency.
Modern HVAC units’ compact design
The compact design of modern HVAC units adds another layer of complexity, making it increasingly challenging to accommodate the high-performance filters needed to improve IAQ to desirable levels. However, the argument could be thrown at the filtration technologies demanding optimal filter performance with massive occupancy space in HVAC units. Ultimately, filtration innovations in filter design, filter media innovations, and aerodynamic and sustainable filter performance, are certainly the order of the day for creating healthier indoor environments for all. That would require addressing challenges such as the increased costs associated with implementing advanced filtration technologies, which might outweigh the benefits of improved air quality? Existing HVAC systems may not be readily compatible with new filtration innovations, limiting their practical application in many buildings. Finally, overemphasising air filtration may overshadow the role of other factors affecting IAQ, such as ventilation rates, leaky envelopes, and patients’ indoor behaviour and emissions.
Airborne pathogen control
Other challenges include airborne pathogen control — particularly during pandemics such as COVID-19. During the recent pandemic, HVAC systems faced increased demands for controlling airborne transmission and excessive patient occupancy beyond the designed capacity of the facilities. Hospitals must adapt by upgrading appropriate and engineered filtration selections and technologies, looking beyond particle capture — including gas-phase and bioaerosol technologies in the filtration plan, ensuring appropriate air changes per hour, and implementing emergency IAQ protocols. Eventually, healthcare facilities must comply with stringent IAQ regulations and guidelines for infection control from organisations such as the ANSI/ASHRAE/ASHE Standard 170 in the US, which provides minimum design standards for healthcare facilities, including specific temperature, humidity, and ventilation for infection control and patient comfort. Among other local and national environmental quality standards that set the stage of what is expected of IAQ, filtration, and HVAC system performance in healthcare facilities are ISO 16000 (IAQ), ISO 7740 (Ergonomics of the thermal environment), ISO 14644 (Cleanrooms and associated controlled environments), and ISO 16890 (Air filters for general ventilation).
In evaluating the overarching hospital environment, it is imperative to extend the focus beyond IAQ considerations to encompass Indoor Environmental Quality (IEQ), as well as the factors of noise, lighting, thermal comfort, and ergonomics. Contemporary healthcare settings increasingly integrate ergonomic principles, which play a crucial role in public health by preventing musculoskeletal disorders and promoting overall wellbeing. Effective ergonomic design in workplaces and communal areas mitigates physical strain, thereby enhancing comfort and productivity. Furthermore, sub-optimal posture may exacerbate the adverse effects of inadequate IAQ, rendering individuals more vulnerable to respiratory complications. Conversely, well-designed workspaces facilitate comfort and concentration, fostering improved respiratory habits. Consequently, the amalgamation of ergonomic principles with IAQ considerations is vital for cultivating healthy and sustainable environments.
In addition to air quality, creating a therapeutic environment necessitates carefully examining various physical factors within the hospital setting. Implementing window and door treatments is instrumental in influencing noise levels, privacy, light exposure, temperature regulation, and hygiene. Innovative solutions, such as integrated louvres between glass, present significant potential to address multiple needs more effectively than conventional alternatives. A comprehensive strategy combining robust IAQ management with astute architectural design and operational practices is essential for establishing safer, healthier, and more supportive hospital environments for patients, staff, and visitors alike.
The art of healing
Additional studies have suggested that balancing natural and artificial lighting through windows and lamps, respectively, can impact patients’ healing process.11,12 However, avoiding temperature fluctuations from external sources through exterior windows is critical to the indoor environment. The appropriateness of HVAC system selection and performance is thus paramount in controlling the climate in terms of temperature and moisture. Climate control encompasses more than just ensuring thermal comfort for human occupants; in a hospital setting, it specifically refers to maintaining the ideal temperature and humidity levels that promote optimal wound healing. These conditions engage chemical reactions and enzymatic processes crucial for effective cell and tissue metabolism during healing. Furthermore, despite efforts to attain the best air quality, the contaminants carried indoors from outdoors represent a risk for infection, even after the treated patient has left the hospital.13-15
The evolving nature of hospital design
The design of hospitals significantly impacts how they are perceived and experienced by patients. Modern hospital environments should not only focus on medical expertise, but also on creating pleasant, healing spaces free of contamination. The evolving nature of hospital design aims to revolutionise healthcare delivery, incorporating elements like tree planting for a calming ambiance. Architects also consider geographical location, topography, weather, and aerosol data in their designs. There is a vision for sustainable hospitals that generate their own power, and use waste as a resource, ultimately striving for a minimal environmental footprint.
The challenge of managing the hospital-built environment lies in engineering and interfacing several parameters in complex building settings. Indoors, healthcare facility design is more complicated than with other building types, and influences HVAC, air quality, and filtration requirements. For example, HVAC requirements for the design of operating theatres range from regulating temperature and moisture to appropriate space pressurisation between adjacent zones. In addition, operating theatres require cleanroom applications, mandating advanced air filtration systems to yield acceptable air quality. Laminar air diffusion represents the final critical step towards achieving thermal comfort by utilising equal clean air distribution in individual zones. Today, technology facilitates testing airflow patterns to minimise the mixing of clean and contaminated air, mainly because airflow can be influenced by various factors. Appropriate air filter selection and regular maintenance of filtration systems are critical, as the consequential pressure rise of HEPA due to particle loading can impede the volumetric flow rates required for healthcare facilities, and specifically operating theatres.
Airborne particles from patients can spread infections and deteriorate IAQ. Visitors’ health also impacts patient and staff well-being. Identifying health issues linked to specific pollutants is challenging, especially with multiple contaminants. Modern hospitals should adopt advanced technologies beyond standard HVAC systems to maintain a sterile environment. A comprehensive strategy for air quality is essential, as neglecting ventilation and maintenance can elevate pandemic risks. Simply changing filters is insufficient; there is a need for research into sustainable air filter options and HVAC performance.
Proper disposal of used air filters, and especially HEPA types, is critical due to the contaminants they contain. Maintenance teams must be trained to handle these filters safely, ensuring hygiene in HVAC systems. Furthermore, continuous air quality monitoring devices are crucial for facility management, allowing data-driven decisions to uphold air quality standards. Investing in these systems is essential for saving lives, and facility directors should prioritise sustainable maintenance over cost-cutting measures.
Conclusions
A comprehensive approach incorporating design, technology, maintenance, and education, underscores the necessity to advance beyond the mere treatment of symptoms associated with inadequate IAQ to rectify the fundamental deficiencies within systems. It is imperative to raise the bar of IAQ, and provide sufficient fresh and clean air to patients, staff, and visitors. These elements are foundational to the future of healthcare, and require addressing the existing gaps in current practices through the integration of advanced technologies, meticulous maintenance, adherence to regulatory standards, and a holistic perspective on the broader indoor environment. Healthcare facilities possess the capability to foster safer, healthier, and more supportive conditions for all occupants. This, in turn, contributes to enhanced health outcomes and operational efficiency. The article serves as a call to action for stakeholders to acknowledge IAQ as a critical strategic priority rather than merely a regulatory obligation.
Dr Iyad Al-Attar
Dr Iyad Al-Attar is a mechanical engineer, air quality consultant, and a Visiting Academic Fellow in the School of Aerospace, Transport, and Manufacturing at Cranfield University for air quality and filter performance relevant to land-based gas turbines. The first associated air filtration consultant for Eurovent Middle East, most recently, he became the Indoor Air Quality (IAQ) patron for Eurovent – ‘the voice of the European HVACR industry with global reach’.
Dr Al-Attar received his engineering degrees (BSc, MSc, Ph.D.) from the University of Toronto (Canada), Kuwait University, and Loughborough University (UK), respectively. His current research at the University of Oxford addresses the importance of air quality inclusion as a rudiment of sustainable urban development. His research is expected to provide a comprehensive ecosystem for engaging HVAC systems to enhance IAQ through appropriate filtration, the deployment of air quality sensing infrastructure, and data sharing with key stakeholders, ‘enabling a human-centred approach and design to understand the air quality they are exposed to and have agency in their overall wellbeing’.
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