Until 2020, Indoor Air Quality (IAQ) was a term associated mostly with indoor air pollution, ambient temperature and humidity. Facilities paid scant attention to what is now the most important parameter – microbial contamination.
Over the last 10 months or so, facility managers and cleaning equipment manufacturers have innovated at a feverish pace to bring out solutions for surface disinfection, which have been embraced wholeheartedly by the market.
Surface disinfection attempts to tackle the resting place of the virus but does not address the fact that it is air that primarily carries the virus from person to person. Air that needs to be purified to break the chain of transmission. It isn’t outside air that needs our attention, nor is it practical to even attempt to purify it. Studies have shown that the risk of transmission is greatest in an enclosed space, thrusting IAQ into the limelight. A recent study suggested that enhancing IAQ could be as effective in reducing aerosol transmission of viruses as vaccinating 50-60% of the population!
To understand how facility managers are tackling this issue,Clean India Journal spoke to Ajaj Kazi, Project Director – Domestic Projects Group at Voltas Limited, both from the manufacturers’ and facility managers’ experience and perspective. He brings decades of experience to figuring how HVAC systems need to be designed and operated to achieve the desired IAQ.
“Earlier, the HVAC system was meant only for cooling; filtration was not given that much importance. Now, filtration is the first priority and cooling comes second”.
When the pandemic broke out”, said Kazi, “There was a lot of confusion initially. People started saying that air-conditioned facilities are going to cause the virus to spread even more.” Readers will remember the total shutdown of all airconditioned facilities, which persisted even after various facilities were allowed to reopen. Disputing the paranoia, Kazi said, “This is a myth. If the HVAC system is properly taken care of, it will not be a medium for viral spread.”
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) – both of which Kazi is associated with – found many ways in which to lower the risk. For example, in dry air, droplets (which contain the virus) evaporate quickly, which means they fall more slowly, remain in the air for longer and travel further. For different reasons, a similar effect is noted at high levels of relative humidity. Hence, the organisations recommend maintaining relatively humidity between 40% and 60%, which is now the gold standard for facilities worldwide.
“The whole HVAC design needs to be relooked at according to Covid guidelines,” said Kazi. “New systems can be redesigned according to new guidelines, but what does one do with already installed systems? There were many malls that were not operating and did not open even after permission was given; we started having Zoom meetings with FM managers about how to go ahead safely.”
The solution? A technology that has existed for the past 120 years, but has emerged in the forefront only now – Ultraviolet Germicidal Irradiation (UVGI).
What is UVGI?
UVGI uses short-wave ultraviolet (UVC) energy – i.e, only a part of the UV spectrum – to inactivate viral, bacterial, and fungal organisms in a way that they are unable to replicate and potentially cause disease. Among the three microbial groups, viruses in particular are most susceptible to UVGI, and more viruses are susceptible than any other microbial group. UVC energy is generated by UV lamps incorporated in devices that are placed near potential sources of contamination. According to Kazi, in practical terms, they are positioned inside Air Handling Units (AHUs) or HVAC ducts. The objective is to distribute UV energy uniformly in all directions throughout the length of the duct or AHU to deliver the appropriate UV dose to air moving through the irradiated zone. Properly designed systems are also able to maintain the cleanliness of cooling coil surfaces and condensate pans.
The letters ‘UV’ immediately remind some people of cancer. Kazi reassured us that UVGI uses controlled UV energy; the controls are tried and tested by reliable labs before being used.
In-Duct Systems vs AHU systems
Kazi recommends installing the UVGI system in the AHU. But in most facilities, the HVAC system has already been installed, and this may not be practical. Here, he recommends the devices be introduced in ducts. In places where neither is possible, he recommended a portable UVGI system which sucks in air with a higher capacity fan, purifies it and sends it back. According to ASHRAE, ‘Economic factors clearly favor an upper-air fixturing when the building being treated with UVC has no air distribution system. When a recirculating central air distribution system is present, a choice becomes possible between upper-air devices, which must be distributed throughout occupied spaces, and in-duct systems, which can be centralized.’ Kazi also described a cart system with UVGI fixtures, which can be moved around to rooms that require disinfection. Each fixture contains two lamps to ensure deep penetration over the surface. Multiple UVGI fixtures in one frame are designed to cover a large surface, disinfecting walls, ceilings, and the floor in one movement, saving cost and time. No pre-design of any system is required; it has a low operating cost, with minimum to no periodic maintenance required.
Where total disinfection is a daily requisite, air filters are needed to complement UVGI. HEPA filters of the MERV 13 class are better at removing particles in the 0.3-1 micron diameter size (the size of many virus particles), and are the gold standard for the Covid times.
But where are the filters introduced? In most facilities, air is purified by them before being circulated; in facilities such as Covid hospitals and ICUs, where the presence of Covid is certain, they are used to purify already circulated air before being released back into the atmosphere – a process called re-entrainment. This is needed to ensure that viral particles from Covid ICUs do not enter non-Covid ICUs and awards.
Kazi said: “During the lockdown, we converted many normal ICUs to Covid ICUs. Normally, we would add a little bit of fresh air before recirculating most of the air. Now, they were converted into 100% fresh air facilities. Many hospitals were in heritage buildings, where modifying the HVAC systems was difficult; solutions differed from site to site.”
“When we take full fresh air into the system, our systems are not designed for such pressure,” said Kazi. “We met doctors and understood that the temperature required inside ICUs was not 21-22 degrees; below 30 degrees is permissible. Based on this, we modified HVAC systems to take care of temperature, pressure and exhaust.” Traditionally, ICUs were positive pressure environments to prevent influx of outside air. Now, negative pressure has been introduced inside ICUs to prevent cross contamination between patients, and to remove exhaust air fully. Kazi warned, “There should be no leakages in the system. When you are taking air back, there is negative pressure and chances of infiltration from other sources.”
Segmentation into zones
Long implemented in pharma, this entails the segmentation of a facility into different pressure zones; air in one zone cannot go to another zone, based on positive or negative pressure, so there is isolation based on air pressurisation.
In containment wards – different from ICUs – it is necessary to pay more attention to the velocity of air in the system; if the contact time of passing air – which is recirculated – is less, then disinfection is less too.
HVAC Maintenance system
“FM has become more techoriented,” said Kazi. “Digital FM can help identify problems, but someone still has to go and fix them. Those who take out filters are exposed to maximum risks and must always be in PPE.”
So far, there is no facility to certify any device usable in HVAC systems as 100% effective against Covid. Hence, following operational and maintenance guidelines is the only way to minimise risk to an acceptable level.
The road ahead
Since more fresh air is being circulated, the HVAC system becomes ‘bigger’. New HVAC systems for the same space will be designed to be bigger too. According to Kazi, this – coupled with spending on UVGI – will increase expenses by 10-15%.
“While the FM team can perform a technical verification of new devices, the higher cost has led to decisions about their acquisition being made at the corporate level. Many offices and malls have called us to retrofit their systems with our products before reopening,” said Kazi.
His final statement encapsulates the magnitude of changes brought about by the pandemic: “The HVAC system has gone through transformation. Earlier, it was only meant for cooling; filtration was not given that much importance. Now, filtration is the first priority and cooling comes second.”