By Benjamin Brits

Medical facilities from rural clinics to large hospitals and surgeries are expected to see continual growth over the next five years, with the most rapid expansion in the private sector in South Africa.

Although the ongoing pandemic continues to have an effect on the world, it has brought to the fore an important aspect of the modern world – healthcare. It has proven that the preparedness of many countries managing a pandemic is lacking, but has also opened doors to fast-tracking improved systems, methods and solutions for the facilities that form the basis for the supply of all medical care.

The considerations for HVAC in a medical facility include elements such as particular temperature conditions – depending on requirement or procedure, filtration – to ensure optimal air quality, humidity levels, space pressures and air flow designs. Most technology today has seen some type of improvement to reduce heat load, and especially lighting, which was historically challenging to work with due to the emanating heat of the types of globes used. You may recall old footage where the assistant frantically wiped and dabbed the perspiration from the doctors to avoid (as best possible) patient contamination.

Without the correct air conditioning, medical facilities in general and complicated surgeries would be extremely dangerous places. So, from a general hospital ward to a neurosurgical procedure theatre, there are what seems to be an endless set of configurations for a facility’s HVAC system that is intended to not only keep patients safe, but everyone working in the facility safe as well. This is from a growing trend in packaged solutions to highly specialised facility designs that are far from mere comfort cooling and heating.

“The essential requirement for air conditioning in any medical facility is to produce the right amount of air in the right condition to achieve the desired result inside any space. In most cases in these applications, affordability is not the question, but rather reliability. An extremely important note here is that we cannot have companies applying commercial grade air conditioning solutions to these types of facilities as we have seen, because they are vastly different,” says Mike Schaefer, director of HCM Contractors.

“Both AHU and packaged solutions are highly-adaptable and can be custom-manufactured to suit the client needs or the space in a plant room.”

In these facilities the HVAC is all about what is not seen. To a patient they wouldn’t have known the difference between a split wall unit in their private room, ducted diffusers from an air handling unit in general areas, or the air quality requirements in a theatre. The correct design solutions are essential, especially when you are dealing with people’s lives.

Today however, everyone is much more aware given what the Covid pandemic has done, and so applying those correct principles will be more important in future to manage outbreaks of any kind. Continual progress in filtration improvements will no doubt also ensue. We are further likely to see the type of technology that was historically reserved for specialist theatres become more widespread into places where many people are expected to gather.

A newly-built isolation ward showing the ‘airlock’ before entering the room. Here, the correct room pressures are essential. Photo by ©Airetronic Maintenance and Sales

Determining facility requirements

In South Africa, medical facilities are considered in two categories, namely the public facilities that form part of government expansion, and then private sector investment. These can be further categorised into clinics, hospitals and surgical theatres, which require different HVAC considerations.

“A medical facility design all starts with, and will depend entirely on, what you want to do at such a facility. When you make an application to build a hospital for example, the facility owners apply for a particular license, and that license will have certain conditions. This could include application for a specific number of hospital beds, theatres, and procedure rooms. The Department of Health then considers various factors and potential demand for a medical facility in the area of interest before issuing any licenses. Once the license is issued, a professional team is appointed to design the facility. A professional mechanical engineer will design the HVAC system based on legislated requirements or in the case of the bigger private groups, in conjunction with their own set specifications they have developed,” says Peter Schilder, director at Saftek Consulting.

Knowing which clinical procedures will be conducted at the medical facility will then allow designers to design the correct type of HVAC. Obviously, air quality is very important, as are temperature ranges to cater to the various possible procedures but further, specialists often require very specific parameters. These include activities where various cements are used that require a particular condition, airflow and humidity level to set correctly. There are also applications where air re-circulation is not allowed at all, that needs to be considered.

Involved standards

HVAC requirements for a medical facility are well-regulated in the local bylaws, regulations, and standards. In South Africa, SANS 10400 covers the minimum requirements for airflow and air changes per hour for various medical applications and also makes allowance for rational design and assumption, as well as adopting of other internationally recognised best practices or standards.

“Further to SANS 10400, a number of local and international documents guide the HVAC design for such facilities – the primary source for design criteria being the ASHRAE standard 170, as it is the most developed document available. Other reference documents have been compiled for this purpose and include the Infrastructure Unit Supply System (IUSS), the Centre for Scientific and Industrial Research (CSIR), R158, British Standards (HTM), and Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA),” notes Jonker Bester, director at Spoormaker & Partners.

Each room type in a medical facility will need to comply to a particular ISO classification (also still referred to as a federal standard). These classifications are according to the ‘cleanliness’ level of the air inside the room by the quantity and size of particles per volume of air, and also refer to the maximum particle concentration limits allowed.

The ISO classification system includes classes: ISO-1, ISO-2, ISO-3, ISO-4, ISO-5, ISO-6, ISO-7, ISO-8 and ISO-9. ISO-1 being the ‘cleanest’ class and ISO-9 is the ‘dirtiest’ class (for reference ISO 9 is still ‘cleaner’ than any regular room or space).

The Federal Standard equivalent for these ISO classes are

FS 100000; 10000; 1000; 100; 10; and 1. This standard was essentially replaced in 1999 by the new ISO classification but is still referred to world-wide in design specifications.

General HVAC considerations

“Although split wall units may have their place in a medical facility environment, they are not ideal for most applications and are erroneously included because of three main factors: they cannot introduce the necessary fresh air into a space, they have no means to filter the re-circulated air that may be contaminated, and they are known to collect bacteria and moulds internally,” notes Schaefer.

Looking at the different ISO/FS classifications, predominantly in South African medical theatres, laminar flow designs which are on the ‘quite clean’ scale environments, are the most commonly installed.

“Reception areas are often a place where HVAC gets neglected, but is one of the places that can hold the most risk with as-yet undiagnosed patients coming in and being admitted.”

“Intensive care units (ICUs) can be safely air conditioned with high air changes and reduced filtration or reduced air changes and increased filtration. Dilution in such an environment is key. Here, we would aim 6 ACH and for anything up to 12 ACH in isolation rooms. Isolation rooms would see a similar ACH with added filtration. Fresh air from outside replacing indoor air is the best way to manage the obvious challenge of possibly concentrated contaminated air,” says Bester.

For general wards and common areas in these facilities, trends show a move towards natural ventilation, ceiling fans and open windows in many cases in both the public and private sectors.

“Reception areas are often a place where HVAC gets neglected, but is one of the places that can hold the most risk with as-yet undiagnosed patients coming in and being admitted. These areas are often ventilated to minimum standard or not ventilated at all. Crowding in these areas creates significant risk of cross-contamination. HVAC design should always consider the effect that a person carrying a highly contagious disease would have on others just by sharing the same space,” adds Schilder.

When it comes to the HVAC control systems, you also don’t want just anyone to be able to set their own temperatures willy-nilly. More often than not, the doctors and nurses require set parameters, but when there is an open door to change set points and fiddle with panels or dials, it is natural for people to want to this, so, limiting any changes to the system should be implemented because consistency is more important.

“Pressures in these spaces simply refer to the principle of either keeping contamination controlled within a space or keeping contamination out of a space.”

You will also find pre-set room modes are common today that will accommodate the specialists working with cements at lower temperatures all the way through to different surgery types and paediatric care at higher temperatures.

“Chilled water systems and steam have always been very popular in medical facilities. Instead of the packaged units that are growing in popularity, chilled water systems can be coupled to various air handling units and the nice thing about chilled water cooling systems is that they are very easy to control, and you will still see these installations at many older hospitals and are still preferred in some installations today,” says Schaefer.

The packaged unit concept has become so popular because these systems can easily be deployed to any location including rural clinics, field hospitals, mobile units, or any remote areas. Packaged units essentially also combine all of the best knowledge and technologies available. Add to this the benefit of replacement of packaged units compared to aged/old chilled water systems mainly pipework.


Positive or negative pressures

Space pressures have for some time been a topic of great discussion, particularly for medical facilities that must decide which areas should be positive and which should be negative, and how to combine designs to ensure risk areas remain controlled.

Pressures in these spaces simply refer to the principle of either keeping contamination controlled within a space or keeping contamination out of a space.

“The latest standards for example require the passageways in a hospital ward to be positively pressurised and airflow to cascade out of the area. This is primarily to keep healthcare workers in a continual safe pressurised fresh air environment. This air may also not be pushed out to where any patients are situated,” notes Schaefer.

The considerations are always around the position to protect the patient or protecting the surrounding environment. Naturally dealing with a very highly transmissible diseases, such as Ebola, you would need to keep the patient in a negative pressure space with double doors and an air lock to maintain an isolated environment.

“Patients recovering from procedures like a bone marrow- or skin transplant are incredibly susceptible to infection. These patients need to be accommodated in a very high quality, clean air environment with positive pressure to make sure that no contamination can get into the room,” adds Schilder.

In some facilities today you will also find clinical areas that have been fitted with the functionality to switch over between positive and negative pressures. There is however concerns in this around the required cleanliness and making sure that your infection protocols are being followed and maintained.

Airflow and ACH

The ASHRAE Standard-170 contains an extensive list of recommended ACH per application type to introduce fresh air into the space as well as the recommended air-recirculation per application (or no air re-circulation). It must be considered that in medical facilities the HVAC system will likely be operating continuously, for 24-hours a day.

Introducing fresh air into a space and exhausting air out of a space also needs careful consideration. In medical facilities, more so than other buildings, the exhaust air must be kept well away from the fresh air intake. In some cases, as it has been alluded to already such as with tuberculosis (TB) facilities, air may not be expelled without the necessary filtration. Location of the hospital also plays a major role when it comes to fresh air as the outdoor air quality is not as consistent as one thinks.

“Introducing fresh air into a space and exhausting air out of a space also needs careful consideration.”

Controlling of air movement is critical from a design aspect from space to space. Correct applied air movement control allows the facility to avoid contamination, and this has been a particular element of focus through the Covid pandemic. This includes the strategy around the facility’s ventilation. As an added challenge, medical facilities have continuously changing occupancy, and would not necessarily be designed to handle a sudden mass of patients, however, adapted designs today allows for different operating modes with the intention of supporting crisis situations.

“One of the bigger challenges within a hospital environment that is seldom considered are lint, fluff and dust from things like hospital linen and gowns. These fine particles, over time, fill up filters and the equipment within the areas. This proves a challenge especially in a theatre for example, where the return air ducts are most commonly installed in the corners of these rooms. Because the inlets are at low levels with unidirectional flows the return air lines pick up everything that lands on the ground. This can affect the air flow rates and require regular maintenance (that often also requires stringent health and safety protocols and the use of hazmat suits),” says Bester.

In theatres, the airflow comprises what is essentially a constant air wash through the laminar flow design principle. “The concept of this design is that you have this constant wash to direct the flow of any bacteria or contaminants into the ducting and take the stale/compromised air away. Some surgeries are naturally more intense than others, where infection can result in the worst outcomes,” adds Schaefer.

Ensuring the correct airflow and recirculation in theatre rooms is another element that can cause challenges for doctors and nurses when considering leakage of anaesthetic gases. On long operating procedures that can be up to 10 or more hours, poor air circulation can result in the concentration of anaesthetic gases, which has been found to affect the teams working in the space. Another property of some anaesthetic gas is their flammability, and hence explosion-risk in confined spaces, however, with modern anaesthetics, this risk has been mitigated.

Humidity control

HVAC systems used in these facilities will always make use of either a humidification process or de-humidification process as no location is the same, so outside air properties as the source of air needs to be managed as well as internal conditions based on particular room effects. Accurate humidity control also helps protect electronic equipment used against possible electrostatic discharges in very low humidity conditions.

Likewise, many semi-conductors and electronic equipment requires closely controlled dry conditions. The presence of excessive humidity or moisture causes corrosion of ‘circuit points’, condensation on a microchip’s circuit surface and improper adhesion of photoresists causing operational failure of the semi-conductor.

Having the correct humidity levels are also not only about patient and personnel comfort. Air humidity that is too low, effectively dry air, has been known to increase and aggravate respiratory problems, and commonly affect a person’s eyes, skin, nose and mouth. These humidity scenarios have also shown to be detrimental to the human immune system. Dry air draws moisture from mucous membranes in the nose and throat, which is one of the body’s main defences against airborne contaminants. As well as increasing the survival rates of airborne viruses, dry air also impairs our natural ability to fight them off.

Air humidity that is too high, wet air, creates an uncomfortable environment and potentially further creates an ideal condition for bacteria and mould growth.

The optimum humidity level in some operating theatre may also depend on the preference of the surgeons involved. For procedures such as open heart or cranial surgery, dry air can promote electrostatic micro-shocks, which can pass from surgeon to patient and are potentially fatal. Typically, the environment during these operations is maintained at 50%RH±5%.

Other reasons for humidity control in operating theatres include preventing delicate membranes drying during stomach procedures, inhibiting the spread of airborne spores during operations involving highly infectious diseases, and preventing evaporation from swabs prior to weighing for more accurate blood loss assessment.

MF005UV-GI is of little consequence if ventilation is inadequate. Photo by ©Saftek Consulting

Other areas of medical facilities that are highly dependent on the correct humidity include MRI suites where electrostatic conditions would again be detrimental, as well as burn units and dressing rooms where the correct humidity assist in dressing changes and in the burn-healing process.

Research, based on the outbreak of the Covid pandemic, has now revealed that the right indoor climate and humidity levels particularly can help limit the transmission of a number of viruses, and plays an important role as an additional protection mechanism.

Studies on the novel coronavirus highlight the effects of air temperature and relative humidity on the virus, and how this impacts its ability to survive on surfaces. The rate of virus inactivation varied across different relative humidity levels, where the greatest level of virus inactivation took place at 50% relative humidity. The virus had higher survival rates at both 20% and 80% relative humidity, so it’s not simply a case of increasing or decreasing the levels: it’s about controlling the climate to very specific parameters. Indications that maintaining an indoor RH% level between 40 to 50% yields the maximum protective effect from aerosolised and settled virus particles. By maintaining these levels, it is possible to contribute to a healthier, safer environment.

New research has also suggested that because the coronavirus is so small and can effectively bypass HEPA filtration in aerosol form, that a controlled increased humidity will create sufficient particulate for the virus to attach to. This then, combined with two or three-stage air filtration and circulation, will enable capturing of the virus within the filter space that could then be further combined with UV-C sterilisation. Speculatively, this process could be used as a space purging programme, or a specific setting if or when required.

Managing air quality

The ultimate goal of supplying and maintaining good air quality then is a combination of the aforementioned topics, and through either the packaged units or air handling unit option, this forms the heart of air into a space as well as the re-circulated air.

Per ISO category and application, there are specific air quality requirements as indicated earlier that determine a maximum particle count and there are further testing procedures that get undertaken in these facilities.

Regular air sampling is conducted through a method known as DOP – or dispersed oil particulate. Also known as filter integrity testing, this process is conducted with the intention of verifying the integrity of any HEPA (High Efficiency Particulate Air) or ULPA (Ultra Low Penetration Air) filters in the system. It involves the introduction of particulates into the system and the particulate count is measured downstream.

Other tests in air quality that are performed regularly are microbial contamination tests where a petri dish with a particular culture is placed on the floor of the space away from any obstacles which is exposed to the air for a given time in order to collect biological particles. This then allows laboratories to measure the ‘harmful’ portion of the microbes in the air.

According to the Trox Technik South Africa team, “Having the support from our international research and development laboratory that have some of the world’s best scientists, allows us to better the industry as a whole, and this is our intention. Once suppliers get given the required design from the mechanical consultant on a project, what is important is not only complying with the specifications but insisting on a quality product. More so because of the environment that AHUs serve in the medical facility environment. The right materials, like stainless steel inside these units, avoid bacteria being able to stick, further, and design benefits such as avoiding awkward angles and cavities where any pathogens or organisms can grow is highly important.”

Both AHU and packaged solutions are highly-adaptable and can be custom-manufactured to suit the client’s needs or the space in a plant room or area which is often a challenge for designers, installers and suppliers.

“Serviceability is actually critical when designing and building any unit that will require maintenance. If you have an operating theatre offline, you need to get it back up and operational very quickly again. Technicians’ understanding of the system is then as important as being able to easily perform maintenance,” adds Schaefer.

Many air handling units will also include gauges to monitor the efficiency of air supply. If the unit is a three stage filtration system, in other words, a primary filter, a secondary filter (which is either a bag or cassette filter), and then a HEPA filter, suppliers will generally provide recommendations to indicate at what pressures filters need to start being replaced to maintain required air volumes. It is possible that filters can become blocked over time and this then may result in air quality compromise as air bypass occurs (basically the air is forced through areas between or around filters and is not filtered).

UV-C technology testing and inclusion in packaged units, ducting and AHUs has already shown indications of positive results, however there are concerns of the unknown outcomes of prolonged exposure to UV-C. Although it has proven successful at neutralising a virus by destroying reproduction possibilities, it is also potentially harmful to other living organisms, animals, and people. Research continues to establish any long-term effects of use. (Note: no factual evidence is yet available as to the effects on prolonged exposure to UV-C or if it will result in any harm at all.)

MF001The air conditioning of a laminar flow operating theatre. Supplied by ©Spoormaker and Partners | Jonker Bester


Maintenance is an area that has been constantly brought up as a major challenge in medical facilities from the lack of skills available, to people working on the HVAC systems that have no clue about HVAC or the components used, to as far as the pure neglect of facility managers. The mentality of “as long as it’s working it’s okay”, does not fit in these scenarios.

“The unfortunate reality in the HVAC world is that the moment you bring in higher technology that is perfectly-suited in the medical field, this is where problems start. The industry challenge is that we don’t have enough people who can fix, maintain, or have the required knowledge to work on these systems. Maintenance needs to be looked at from a different perspective,” says Schaefer.

Trox shares the same sentiment, adding, “Over the past 10 years there has been a drastic reduction in the quality of maintenance work and lack of maintenance has long-term effects for medical facilities. The simplest example of this is what is known as ‘sick building syndrome’ that can be traced back directly to poor maintenance strategies.”

Schaefer adds, “We have seen so many failures as a result of poor or no maintenance. For this reason, we have spent years developing systems to allow easy maintenance. Our packaged units for example have been designed (with the permitting components) so that they can actually be sprayed down internally while all electrical and mechanical parts are located on the outside.”

“Some facilities are worse than others when it comes to maintenance and this is due to a range of issues – from inadequate maintenance budgets to just plain lack of knowledge. There are facilities that have impeccable maintenance strategies with properly trained technical staff and engineers, but the latter is less common. One particular challenge in maintenance that comes to mind is the maintenance records that need to be kept, but sadly, too often they are not,” says Schilder.

Schilder continues, “I recall assessing a TB-care facility and checking the air flow in various rooms, as is required by law from time to time, and discovering that there was no airflow. On further investigation, I found that when the facility was upgraded the technicians doing the electrical work didn’t know where the ventilation fans were supposed to be connected, so just left them disconnected. There was no ventilation at all for years! These are real scenarios in medical facilities that need to be addressed.”

Maintenance still requires someone to go and clean the filters and AHUs, and who knows what lurks in those areas. These are the direct areas where everything is concentrated – viruses, bacteria, mould, skin cells, and more, and it’s a dangerous task for the poor technician to go and sort out, and even more so when maintenance is unduly prolonged.

“Not wanting to be overly alarmist, if you don’t have the right ventilation strategies in place, healthcare facilities can become very risky buildings. We must always keep in mind when designing and operating healthcare HVAC systems that we have become part of a global village with people travelling here from all over the world, potentially bringing with them any type of pathogen. Everyone is now rightfully focused on Covid, but the reality is that other outbreaks can become a reality at any time. Any patient can walk into a facility at two o’clock in the morning and the staff may have no idea that this could be the start of a next pandemic. A healthcare facility’s ventilation system is the first (unseen) barrier of protection against contamination of staff and patients that are already vulnerable. Designing and maintaining these systems require the attention and expertise it deserves as part of the healthcare chain,” concludes Schilder.


HCM Contractors
Saftek Consulting
Spoormaker & Partners
SMAC Enterprises and Munters White Paper
Trox South Africa