The ASHRAE Falcon Chapter (UAE – AFC), in cooperaBon with HawaQ, conducted a webinar on June 5 to discuss ASHRAE Standard 241, with an emphasis on balancing the need for good Indoor Air Quality (IAQ) with energy efficiency. The online seminar delved into approaches to sustainably manage infecBous aerosols and to uphold superior IAQ.

The marquee speakers were Dr William Bahnfleth, Fellow/PresidenBal Member ASHRAE, and principal author of ASHRAE Standard 241; Dr Marwa Zaatari, Associate Member ASHRAE; Dr Lidia Morawska, DisBnguished Professor at QUT; Abdulaziz Jaffer, Health and Safety Department, Dubai Municipality; and Erik Malmstrom, CEO, Safetraces. Osama Al Masri of the ASHRAE Falcon Chapter was the moderator.

Dr Morawska, speaking first, spoke on the importance of looking at the cost benefits of chilling the air. For any New ConstrucBon, she said, whatever the currency that is spent on designing be`er buildings, there is a USD 10 benefit, so it is somewhat easier to calculate in the case of New ConstrucBon. Retrofibng ExisBng Buildings for IAQ, on the other hand, she said, poses a few challenges. “But, there is a huge opportunity for improving IAQ,” she said.

Dr Morawska, speaking on the extent of the benefit of be`er IAQ, pointed to an arBcle on China in The Lancet that appeared in 2023. “The corresponding financial cost of IAQ polluBon was USD 411 billion,” she said. “It accounted for over three per cent of China’s GDP for residenBal houses.” The situaBon is not unique to China, she said. Indeed, it could be compared to other countries.

Dr Morawska said it is important to have IAQ-related guidelines. Generally speaking, she said, guidelines focus on protecBon of the human populaBon from air polluBon; they are based only on health. IAQ standards, though, are different, she said. They include addiBonal compliance parameters. They focus on the difference between indoor air and outdoor air. And every indoor space is different in terms of concentraBon of pollutants. We cannot use bulky and expensive compliance-monitoring devices in all IAQ-related situaBons, she said.

Dr Morawska spoke of the need for measuring various parameters. Ingress of outdoor pollutants includes dust storms and traffic-related emissions, she said; they are not only pandemic-related. Keeping this in mind, she proposed a consensus document (see Table 1) that could be a blueprint for good IAQ.

Different jurisdicBons may choose different values, Dr Morawska said, but once they modify, they can use the blueprint.

Dr Zaatari, speaking aker Dr Morawska, emphasied the need for building resilience against not only airborne diseases but also wildfires. She spoke of a paradigm shik that intertwines health and wellness and also consideres decarbonisaBon. Building health should not come at the cost of decarbonisaBon, she said.

Speaking specifically on ASHRAE Standard 62.1 that was updated in the last few years to provide high IAQ even in normal mode, she said most US states have adopted it. Giving the 62.1 perspecBve – definiBon – on venBlaBon, she highlighted that it is not just outdoor air. “It is a combinaBon of outdoor air and air that has been cleaned,” she said.

Then, speaking on VenBlaBon Rate Procedure (VRP), Dr Zaatari characterised it as a prescripBve approach. The VRP concept, she said, depends on diluBons to improve IAQ. Most buildings today ensure be`er IAQ through permibng more condiBoned outside air to “refresh” the indoor air, she said. This, she added, results in an increase in operaBng costs for the building owner and higher greenhouse gas emissions through the use of larger and more expensive HVAC systems. But what if the outside air itself is polluted, she asked, adding that the world must accept the fact that outdoor air might not be fresh air. PoinBng to the WHO PM limit as being 5 micrograms/m3 as an example, she said it is higher outside. “So it is be`er to keep it outside,” she said.

Compared to VRP, IAQP (Indoor Air Quality Procedure) is a be`er approach, Dr Zaatari said. IAQP is a performance-based approach, she said. “It allows less outside air when incorporaBng source control and/or filtraBon and air cleaning,” she said. It is equivalent or be`er than VRP, especially when outside air is polluted, or unusual contaminants are present.” She said the energy consumed through IAQP is oken lower, because a porBon of the outside air is replaced with cleaned indoor air. In terms of cost, she said IAQP paves the way for lower operaBng expenses through energy savings and lower capital equipment costs from HVAC load reducBon.

Addressing the word doing the rounds that IAQP is complicated, she said that ASHRAE in May 2024 introduced an IAQP Calculator. It is simple to use, she said, because all that the user needs to do is to enter inputs, like square footage, and the calculator does the rest.

PoinBng to another objecBon – “Would reducing the intake of outdoor air not lower the intake of oxygen?” – Dr Zaatari said the outdoor concentraBon of oxygen is 21%

If the venBlaBon rate equals 16 cfm/person, she said, the oxygen concentraBon indoors is 20.9%. If the venBlaBon rate equals 5 cfm/person, the oxygen concentraBon indoors is 20.8%. In other words, she said, the figures represent the same effecBve oxygen rate if one went into the 12th floor of a building. “The change is minimal,” she said. “Playing with outdoor air within these limits is not going to affect oxygen concentraBon, indoors.”

Dr Bahnfleth, then speaking on the topic, “ASHRAE Standard 241-2023 Conrol of InfecBous Aerosols” laid the foundaBon for his presentaBon by defining infecBous aerosols as airborne parBcles containing acBve pathogens capable of causing infecBon. These aerosols, he said, are produced by respiratory acBviBes and come in a wide range of sizes. The largest parBcles, he said, se`le rapidly, whereas the smallest parBcles remain suspended in the air for longer periods of Bme.

Dr Bahnfleth said it became quite clear aker the experience with the pandemic that the damage from such diseases arises when they are novel and varied like COVID was. He said the purpose and scope of the standard is to establish minimum requirements for controlling infecBous aerosols to reduce the risk of airborne disease transmission. The standard, he said, applies to non-residenBal, residenBal and health care faciliBes, ExisBng Buildings, New ConstrucBons, renovaBons and addiBons. The standard, which he said addresses long-range transmission, proposes equivalent clean air flow for InfecBon Risk Management Mode (IRMM). He said the standard does not replace minimum acceptable IAQ standards.

Addressing IRMM specifically, Dr Bahnfleth described it as the mode of operaBon in which measures to reduce infecBous aerosol exposure, documented in a Building Readiness Plan, are acBve. Answering the quesBon, “Why not all the Bme?” he said doing do would mean a potenBal increase in energy use and cost. Also, the risk of infecBon and consequences of infecBon, he said, would vary over a wide range.

With that established, he said, it is up to public health officials, owners of buildings and occupants to decide when to switch on to IRMM. “We are pubng resilience into IAQ standards with 241,” Dr Bahnfleth said by way of explaining IRMM.

Explaining Equivalent Clean Airflow (ECA), Dr Bahnfleth said the flow rate of pathogen-free air, if distributed uniformly within the breathing zone, would have the same effect on infecBous aerosol concentraBon as the sum of actual outdoor airflow, filtered airflow and the inacBvaBon of infecBous aerosols.

Then, speaking on air cleaning – one of the key aspects of the standard, he said the aim is to reduce infecBous aerosol concentraBon through capture and removal or inacBvaBon. Air- cleaning technologies, he said, would include mechanical filters, germicidal ultraviolet light, ionisers and photocatalyBc oxidaBon. “MenBon of specific technologies in the standard,” he clarified, “is not endorsement.”

Dr Bahnfleth said the goal of the standard is to create a level playing field for all technologies. Saying that lack of informaBon and standards relaBng to air-cleaning systems was a major problem during the COVID pandemic, he added that it is essenBal to test for effecBveness and safety of the intevenBons. He defined effecBveness as the ability to remove or inacBvate infecBous aerosols and safety as prevenBng any adverse effects from direct exposure (UV-C, oxidants) and secondary contaminants (parBcles and ozone).

Then, speaking on the benefits of basing requirements on ECA, he elaborated on the importance of quanBfying the combined effect of all controls – outdoor air and air-cleaning systems. He also spoke of the need for enabling the use of alternaBves to outdoor air to reach targets, which he added would provide be`er flexibility to meet objecBves and lower the energy use of soluBons.

Speaking aker him, Jaffer from Dubai Municipality said IAQ ma`ered a lot in Dubai and in the UAE, considering that people spend up to 93% of their Bme indoors. Dubai’s climate, characterised by hot summers, and extensive use of air condiBoning can impact IAQ, he said. Rapid urbanisaBon and construcBon acBviBes, he said, contribute to indoor air polluBon.

Saying that Dubai Municipality is commi`ed to ensuring good IAQ, he said the government agency pioneeded the first-of-its-kind regional technical guide for IAQ, which provides best pracBces for building owners and occupancts for maintaining healthy indoor environments.

The Dubai Municipality, Jaffer said, acBvely conducts various studies and projects relaBng to IAQ. These studies, he said, focus on criBcal areas. Dubai Municipality, he said, incorporates the resulBng insights into regulaBons and daily monitoring acBviBes.