Coronavirus Air Filtration Update - March 12, 2020


Can Coronavirus Spread through HVAC System?

The CDC does not believe that COVID-19 is likely to be transmitted through duct work. However, several university studies show the opposite. Coronavirus could spread around buildings via air conditioning systems or even on a draft, new analysis has suggested after scientists found traces of the virus in a hospital air duct. The results from swab analysis of the rooms used by three coronavirus patients indicate that the disease may be more contagious than previously thought.

Even though the patient thought to be responsible was suffering only "mild" symptoms, scientists from the National Centre for Infectious Diseases in Singapore found evidence of the virus in the hospital's air exhaust. This "suggests that small, virus-laden droplets may be displaced by airflows and deposited on equipment such as vents", they said.


New Air Filtration Needs for Autopsies

In Iran bodies are piling up at morgues. This presents several challenges. Autopsies on decedents with known or suspected COVID-19 should be conducted in Airborne Infection Isolation Rooms (AIIRs). These rooms are at negative pressure to surrounding areas, have a minimum of six air changes per hour (ACH) for existing structures and twelve ACH for renovated or new structures, and have air exhausted directly outside or through a HEPA filter. Doors to the room should be kept closed except during entry and egress. If an AIIR is not available, ensure the room is at negative pressure with no air recirculation to adjacent spaces. A portable HEPA recirculation unit could be placed in the room to provide further reduction in aerosols. Local airflow control (i.e., laminar flow systems) can be used to direct aerosols away from personnel. If use of an AIIR or HEPA unit is not possible, the procedure should be performed in the most protective environment possible. Air should never be returned to the building interior, but should be exhausted outdoors, away from areas of human traffic or gathering spaces and away from other air intake systems.

Transmission through Cruise Ship Ductwork Diamond - Princess Ductwork Debated

Anne Schuchat, principal deputy director at the U.S. CDC, says there is no current evidence to suggest that the coronavirus spreads through air-handling systems. Eric van Dijk, employed at Dutch HVAC specialist Heinen & Hopman, agrees it is unlikely for viruses to spread through a ship’s HVAC system due to the way air travels through the system.


The cruise ship Diamond Princess was quarantined in Japan. The ship had 3700 people on board, of which 620 people were eventually infected by the coronavirus. Some of the passengers expressed worries about the virus spreading through the ship’s HVAC (heating ventilation air-conditioning) system to which the CDC responded.

According to Van Dijk, whose company did not supply the HVAC system for this ship , ‘fresh air is supplied on a cruise ship by several air handling units. The ducts connected to the air handling units provide the public areas and cabins with fresh air. Within these units, air passes through multiple filters, at least EU4 pleated filters.’ EU4 filters belong to the category of coarse dust filters with an over ninety per cent arrestance.

‘Optionally, these units are equipped with a HEPA filter and/or UV light units to treat polluted air further,’ adds Van Dijk. These filters do not stop viruses from spreading, however.

Van Dijk explains: ‘The filtered air that enters a cabin is filtered again in a fan coil unit, but these filters are made to fight bacteria, not viruses. Viruses are so small, that you would need a very strong filter. When you need such a strong filter, the air handling units are possibly four times as big. This means that the energy consumption and emissions will be many times higher.’ Not something that is desirable for a cruise ship, as these ships already have a name for being polluters and are working hard to lower their environmental footprint.

The system on board the Diamond Princess was supplied by MCI Namirei. In a statement, Diamond Princess’ owner Princess Cruises said, ‘the HVAC filtration system on our ships is comparable to those used by land-based hotels, resorts and casinos.’ This probably means this system will also not be able to filter out viruses.

However, Van Dijk points out the chance of a virus spreading through the HVAC system is still very small. This has to do with the way the air travels. He has drawn the overview which shows that, although not impossible, it is unlikely for a virus to travel from cabin A to cabin B.

The opposite conclusion was reached by Qingyan Chen, Purdue’s James G. Dwyer Professor of Mechanical Engineering. He has researched the spread of air particles in passenger vehicles and how to track them. His team developed models in the past for showing how the H1N1-A flu and other pathogens travel through aircraft cabins.

When Chen co-led the Air Transportation Center of Excellence for Airline Cabin Environment Research, his lab made discoveries about the airborne nature of SARS that could inform understanding of the coronavirus.

Chen’s lab is currently developing a ventilation system that would prevent the spread of pathogens by allowing each person to breathe in only his or her own air.

He told the media  “It’s standard practice for the air conditioning systems of cruise ships to mix outside air with inside air to save energy. The problem is that these systems can’t filter out particles smaller than 5,000 nanometers. If the coronavirus is about the same size as SARS, which is 120 nanometers in diameter, then the air conditioning system would be carrying the virus to every cabin.

Cruise ships could minimize this problem by just using outside air and not recirculating it.”


Biosafe Air

The effectiveness of HEPA and Filtrete filters was addressed by Biosafe Air.  How effective can HEPA actually be? The chart below, adapted from an EPA report lists the MERV rating of filtration material corresponding to the typical contaminant that they address, along with the typical filter type found in the MERV rating group (from HEPA to “HEPA-like” filters).

Even though the MERV value is strictly performance based, you can still derive some value from the chart below, as it gives you an indicator of the limits of certain types (e.g. higher efficiency pleated filters vs. true HEPA filters). Generally, HEPA is considered the equivalent of a MERV 17.

Reputable air purifier companies that have filtration-based units should clearly state their MERV rating, or state plainly what the particle size and type of contaminant their product can actually address.


 Biosafe Air uses the 3M products.


Camfil supplies air filters and systems for many applications including the most severe. “There are more than 60 biosafety laboratories classified as Level 4 (highest risk) by an international commission. Camfil has already delivered containment solutions for many of them in China, France, Switzerland, Germany and the U.S.A.

Camfil has issued some guidance relative to coronavirus at  This website also has links to CDC and ASHRAE guidance documents.


Livsdal  has intensified the development of a more affordable and smaller version of its premium air purifier. The new air purifier under the name Essential will have the same capacity of capturing molecular gases like formaldehyde, nitrogen dioxide and ozone in the size of 0.5 nanometer particles, viruses like SARS-CoV-2 that is 10 nanometer. Viruses are in general in the size range from 10-400 nanometer that is equivalent to 0.01-0.4 micrometer. It will also capture allergens, smoke, dust, pollen, bacteria, odor, dander, mold to mites in the size all the way up to more than 10,000 nanometer. The Essential is critical equipment suitable for hospitals, health clinics, nursing homes and dental offices, as well as in homes of all people vulnerable to air pollution. It is designed to effectively capture pollutants in rooms up to 75 square meter. The height is 100 cm times 40 x 40 cm. Livsdal will start to accept pre-orders with delivery in autumn 2020.

The purifiers incorporate seven long lasting, high capacity and high quality filters.

  • Pre-filter-Catches regular dust and larger particles
  • HEPA 13 Particle filter-Captures dust, bacteria and viruses among many other particles. 99.996 % efficiency for particles of 0.3 μm and will capture particles down to 0.005 μm.
  • Carbon Molecule filters-Different activated Carbon Molecule filters capture toxic gas molecules as small as c. 0.0005 μm. They are designed to absorb odors, gases and car emissions including nitrogen dioxide, sulphur dioxide, ozone, formaldehyde plus a list of other compounds – all tested to ISO 10121.
  • Post filter-The final safeguard comes in the form of a metal granular-filter, located on the fan outlet to capture any carbon particles that are released.

Johnson Controls

A team from Johnson Controls went to Wuhan to meet the emergency needs of a people hard hit by the novel coronavirus outbreak. The Johnson Controls team was working hard to help Taikang Tongji (Wuhan) Hospital construct a makeshift hospital. 

It took just 45 minutes for the Johnson Controls team to make the key arrangements and plan for this mission, which was to provide full support for building the infrastructure of the makeshift hospital, including the communications system, the safety system and the elevator alarm system.


Johnson Controls engineers testing the IT equipment and installing wireless access points


Within twelve hours, the company's first batch of medical protective supplies such as protective clothing, goggles, and masks had arrived. At the same time, colleagues from all over China sent forth material goods and well wishes to support the team. 

On February 9 the Trion air filters were delivered.



Viruses can typically range from 0.01 to 0.2 micron in size, although they may cluster or attach to larger particles. How effective are Pall HEPA filters at removing bacteria and viruses? An independent test laboratory has tested three Pall cabin air filter elements using two different bacteria; Brevundimonas diminuta and Bacillus subtilis and results show that the bacterial removal efficiency of the Pall cabin air filters is greater than 99.999%. Similarly, when challenged with the MS2 Coliphage virus, the virus removal efficiency of the Pall cabin air filters is also greater than 99.999%


Pall Aerospace engineers teamed up with scientists from Pall Medical group to develop and validate the microbial removal efficiency of aircraft cabin air filters, following standard practices used in the healthcare and pharmaceutical industries.

Why cabin air filters do not need an anti-microbial treatment? In free air, most microbes die within a few minutes. Once captured by the filter media, the survival rate of microorganisms in the aircraft environment is very low. Most bacteria require high humidity and a source of nutrition to survive. The conditions typically found in the aircraft recirculation system are 10-15% relative humidity and lack of a source of nutrition. Is there a danger to maintenance personnel by removing used cabin air filters?

There is no more risk involved in replacing a cabin air filter than carrying out general maintenance on any aircraft part that has been in service for a number of years. Maintenance staff should wear the same personal protective equipment as for other aircraft maintenance tasks which require protection against dust, and per the local regulations. The used HEPA filter should be placed and sealed in a plastic bag. A specific biohazard bag is not required for disposal of the HEPA filter in most jurisdictions.

Peco Filter

PECO filter effectiveness was evaluated by Consumer Reports.  Their analysis follows:

“Like so many brands that trend on social media, the Molekule Air is available only through the manufacturer’s website—for a whopping $800. It’s the sort of niche product that Consumers Reports wouldn’t necessarily test, but given the buzz it’s generated, “we felt a responsibility to weigh in with test data”.

“And because the Molekule manufacturer claims to have revolutionized air cleaning with its proprietary PECO technology, we dug a little deeper. Here’s the story of our reporting and our lab tests.

This acronym is short for photoelectrochemical oxidation. It isn’t new technology, per se, but rather a boosted version of PCO (photocatalytic oxidation), which has been used for decades to clean contaminated air and water. 

A typical mesh filter—HEPA, for instance—captures only airborne particles. PECO and PCO, however, take it one step further and also target gases. It does this by coating filters in a catalyst (PCO usually uses titanium dioxide) that reacts with UV light to oxidize gaseous pollutants and breaks them down into harmless molecules.

According to the Environmental Protection Agency, PCO air cleaners can break down many types of gaseous pollutants, but not many typically found in indoor air. The process can also react with some pollutants to generate other dangerous byproducts, such as ozone, formaldehyde, nitrogen dioxide, and carbon monoxide.

Because of these factors, the EPA reports that to effectively and efficiently eliminate common gases and microbes found in homes in a safe manner, PCO technology needs to improve. Molekule says it has done just that.

“PECO was inefficient in destroying pollutants, so we fine-tuned all the parameters,” says Jaya Rao, Molekule’s COO and co-founder. “PECO innovations happened on many levels: the chemical coating, the filter, as well as the UV lighting.” Working together, she says, these innovations make PECO work faster and more efficiently than PCO, allowing it to destroy gases, bacteria, viruses, and mold spores—without producing any harmful byproducts. Rao declined to go into detail about what the company uses for the catalyst.

CR tests for particle reduction and not for gas or microbe removal. James Dickerson, CR’s chief scientific officer, was asked whether Molekule’s claims have any merit.

“Theoretically, PECO could work to eliminate microscopic airborne molecules,” Dickerson says. “But our tests show that the Molekule Air is not proficient at catching larger airborne particles, which ultimately means it’s not getting enough air passing through the system.”

We put the Molekule Air through our standard battery of air purifier tests, and it almost flunked: We put it into a sealed chamber and injected particles as small as 0.1 micron and up to 1 micron into the room—a range that includes dust mite allergens, cat allergens, smog, smoke, and atmospheric dust. (For reference, human hair has a diameter of 100 microns). A particle counter measured the change in air-particle concentration as the machine ran for 15 minutes. As usual, we tested at the highest speed and again at a lower speed.

The Molekule Air gets a Fair rating for smoke and dust removal at high speed and a Poor—the lowest score possible—at low speed. It is the third-lowest-scoring air purifier of the 48 we tested. The manufacturer says the Molekule Air is sized for rooms up to 600 square feet, but its performance in our tests ranks it among compact models that are designed for small rooms. Based on our lab’s calculated rate at which it can process the air, the Molekule Air wouldn’t be able to handle any room larger than 100 square feet.

We shared our methodology and findings with Rao, and she took issue with our testing.

“It’s a very limited assessment of Molekule because instantaneous removal of particles is not the full picture of what air purification looks like,” Rao says. “And while we may be destroying at a slower rate, we’re still doing something much more complicated, which is truly purifying the air at the nanoscale level and making it safer.”

But if the Molekule Air isn’t pulling enough air into the machine in the first place, it may struggle to clean the air at any scale. “Even if the PECO filter works and it purifies the air of microscopic particles, it’s still not effectively catching the large particles, which are also irritants,” Dickerson says.

In addition to the Molekule Air’s poor performance in our testing for particle reduction, there’s the price to consider. The Molekule Air costs $800, with an annual cost of $130 for filter replacements, plus an additional $50 a year for energy use, based on our calculations. (The model is not Energy Star certified; unlike the majority of air purifiers we test.)

It’s also not very quiet, garnering a Fair score for noise on the high-speed setting and a Good score on the low-speed setting. Our verdict? Pass on the Molekule Air and opt for one of CR’s recommended air purifiers. Consumers Report say there  are three models, that perform well in  particle removal tests and cost hundreds less. air purifier buying guide.

Terra Universal

Terra Universal has a range of portable cleanrooms, air showers and  U.V. Sanitizing modules as shown below.


Vanguard Healthcare Solutions

A portable operating theatre has been set up in the car park of one of Australia's biggest hospitals.

Surgeons at Melbourne's The Alfred Hospital have been performing life-saving procedures in the 'Laminar Flow Operating Theatre' after a storm wreaked havoc on one of their primary theatres.

Vanguard mobile operating theatres can offer a significant increase in capacity during times of refurbishment or increased clinical need. A Vanguard theatre gives hospitals a reliable, safe answer to capacity pressures across a range of specialties and procedure types. Mobile laminar flow operating theatres have been widely used across the NHS for procedures including hip replacements, knee replacements and joint revisions. Vanguard laminar flow theatre facilities offer HEPA-filtered environmental air that conforms to Grade A EUGMP, with up to 600 air changes per hour passing over the patient, and 25 fresh air changes.


The World Health Organization says that managing an epidemic calls for partnerships with service providers who can help healthcare providers such as hospitals add capacity – preferably partnerships that have been established in advance. This means they can call on them more speedily should disaster strike, and everyone knows what’s expected of them.

In the disaster movies, Vanguard sees public spaces being used as temporary healthcare settings when epidemics hit – sports halls, community centres and the like – but this is not ideal for patients, their families, or the staff treating them.

So, what else would work? Clearly, building extra hospital or additional clinical spaces from bricks and mortar isn’t an option – so what can be done? Organizations such as Vanguard Healthcare Solutions work alongside healthcare organizations to create extra capacity which is temporary but much more robust and absolutely clinically sound. The environments are not temporary, but they can be temporarily used.

In an epidemic, units can be quickly deployed to support areas which are struggling to meet the increased demand, or where, if space has been commandeered in one hospital to create a ‘hub’ for the treatment and containment of an epidemic, they can be used to create a more long-term ‘back-up’ in other locations to make up the shortfall – for example for dialysis patients.

Patients in either instance can be decanted to the mobile solution – whether that is a clinic, a ward or an operating theatre. Or if additional or faster turnaround of sterile equipment is required to meet the increased demand, a mobile central sterilization unit can help to bridge the gap.

The mobile units create spaces which can be, if necessary, completely separate from the hospital creating an infection control ‘oasis’, or can be used for testing, triage or supporting the ‘walking wounded’ in clinics and wards. They can be used as additional ward space or even, if needed, a welfare area for staff who may have to stay on site for an extended period without going home. They can also be used for additional and self-contained morgue space, minimizing the cross-contamination risk.


ASHRAE Provides Guidance

In response to ongoing developments, ASHRAE has released proactive guidance to help address coronavirus disease 2019 (COVID-19) concerns with respect to the operation and maintenance of heating, ventilating, and air-conditioning systems.

The ASHRAE COVID-19 Preparedness Resources webpage provides easily accessible resources from ASHRAE to building industry professionals.

“The recent escalation in the spread of coronavirus disease 2019 is alarming on a global scale,” said 2019-20 ASHRAE President Darryl K. Boyce, P.Eng. “While ASHRAE supports expanded research to fully understand how coronavirus is transmitted, we know that healthy buildings are a part of the solution. ASHRAE’s COVID-19 Preparedness Resources are available as guidance to building owners, operators and engineers on how to best protect occupants from exposure to the virus, in particular in relation to airborne particles that might be circulated by HVAC systems.”

Available on the webpage is ASHRAE’s recently approved position document on Airborne Infectious Diseases. The Society’s position is that facilities of all types should follow, as a minimum, the latest practical standards and guidelines.