Frequently Asked Questions

Does ultraviolet germicidal irradiation (UVGI) kill SARS-CoV-2, cold and flu viruses?


Ultraviolet germicidal irradiation (UVGI), otherwise known as germicidal ultraviolet (GUV), is a disinfection tool used in many different settings –  — residential, commercial, educational, and healthcare.

The technology uses ultraviolet (UV) energy to inactivate (kill) microorganisms including airborne viruses – flu, cold, RSV and Covid.

Can HVAC filters effectively capture SARS-CoV-2, flu and cold viral particles?

 Filters for use in heating, ventilation, and air conditioning (HVAC) systems are generally tested under procedures outlined in ANSI/ASHRAE Standard 52.2-2017-Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. This standard was developed by ASHRAE, a global society focused on building systems, indoor air quality, and sustainability in the built environment, and is available for free online viewing during the ongoing pandemic. Based on the filtration efficiency determined by the testing procedures, filters are assigned a Minimum Efficiency Reporting Value (MERV). The MERV provides a measure of the “filter efficiency” over the range of particle sizes prescribed in the test procedure. MERV values range from 1 to 16 and higher MERV values correspond to more efficient filters.

UVira IAQ Note: Most residential HVAC filters are MERV 8.

Research shows that the particle size of SARS-CoV-2 is around 0.1 micrometer (µm). However, the virus generally does not travel through the air by itself. These viral particles are human-generated, so the virus is trapped in respiratory droplets and droplet nuclei (dried respiratory droplets) that are larger than an individual virus. Most of the respiratory droplets and particles exhaled during talking, singing, breathing, and coughing are less than 5 µm in size. CDC recommends using the highest efficiency ventilation filters possible, without having detrimental effects on overall HVAC system performance.

ASHRAE has similar guidance; however, they recommend a minimum filtration efficiency target of MERV 13, provided there are not substantial negative impacts on the HVAC system performance and occupant comfort.

UVira IAQ Note: Modern HVAC systems are not designed to circulate air through MERV 13 filters. As MERV filters are denser in order to catch smaller particles, the blower motor has to work much harder to force the air through the filter. See our solution below.

A MERV 13 filter is at least 50% efficient at capturing particles in the 0.3 µm to 1.0 µm size range and 85% efficient at capturing particles in the 1 µm to 3 µm size range. Collectively these particles are capable of remaining airborne for hours and are most associated with deep lung penetration. A MERV 14 filter is at least 75% and 90% efficient, respectively, at capturing those same particles. Efficiencies for MERV 15 and MERV 16 filters are even higher. Thus, the recommended filters are significantly more efficient at capturing particles of concern than a typical MERV 8 filter, which is only around 20% efficient in the 1 µm to 3 µm size range and is not rated for capture efficiency of the smaller 0.3 µm to 1.0 µm particles.

Increasing filtration efficiency can increase the pressure drop across the filter. This can lead to increased fan load (the fan has to work harder and use more energy), reduced airflow rates, and/or issues controlling indoor temperature and relative humidity levels. Scientific developments in filter design and manufacturing have reduced the amount of the increased pressure drop and its resulting impact on HVAC operations, but not all filters have adopted the newer technology.

Prior to a filtration upgrade, the specific filters under consideration should be investigated for their pressure drop ratings at the flow rate(s) of intended use and the potential impacts of that pressure drop evaluated against the capabilities of the existing HVAC system.

UVira IAQ Note: Our polarized media filter has the density of the usual MERV 8 filter so the blower motor operates normally. However, as our media filter is polarized, it filters the air passing through it as if it were a MERV 16 filter.

High-efficiency particulate air (HEPA) filters are even more efficient at filtering human-generated infectious particles than MERV 16 filters.

UVira IAQ Note: We have a whole house HEPA unit for residential installation.

What are the benefits of clean air for my office or store?

Joseph Allen, an environmental health expert who founded the Healthy Buildings program at the Harvard T.H. Chan School of Public Health, argues that the payoffs outweigh these investments by several orders of magnitude.

In a 2015 publication modelling costs and benefits of doubling office buildings’ ventilation rates, Allen and his co-authors found businesses had a lot to gain from relatively small investments in workers’ air quality.

The benefits: lower rates of absenteeism and sick leave, lower health care costs (as a result of lower incidence of health care use due to influenza, pneumonia, and other respiratory infections), and higher productivity due to better cognitive performance and productivity.

“When we do the economic analysis,” said Allen, “we show that the cost is on the order of tens of dollars per person per year — against benefits of six to seven thousand dollars per person per year.”

What is sick building syndrome?

The Covid-19 pandemic, spread by an airborne pathogen, prompted demands for a paradigm shift in the way we think about air quality. Now more than ever, it’s clear what we have to gain from improving indoor air quality: Not only could doing so help mitigate the next pandemic, but it could also lead to other large-scale improvements in health and productivity ……

Humans have been using fresh air to cure and prevent disease for as long as we’ve understood diseases to be something other than punishment from the gods. But where we encounter clean, fresh air has changed with time and technology.

In the early 1900s, buildings were generally constructed of wood, stone, clay bricks, and other natural materials that generally did not emit airborne toxins — and they were drafty, often allowing outdoor air to circulate whether people wanted it or not. Over the course of the next century, the building blocks of modern construction changed: Plastics were the future, and new or renovated buildings began incorporating contemporary materials like synthetic carpets and glues, pressed wood products, and vinyl into their designs — and with them, a variety of toxic compounds they silently emitted.

Meanwhile, the global energy crisis of the 1970s incentivized architects and engineers to design buildings that were increasingly airtight — why pay money to heat a building just to see that heat escape out a crack around a window? That, in turn, required new approaches to controlling their interior climates. Mechanical systems for heating, ventilation, and air conditioning (HVAC) became more common, as did open-plan layouts to allow for better air circulation.

Every day, people entered sealed buildings held together with solvents, adhesives, particle board, drywall, and all of the chemicals that came with them. Reports of “office illness” crept into the media, and in the early 1980s, the World Health Organization coined the term “sick building syndrome” to describe the constellation of symptoms caused by the invisible byproducts of modern construction.

The structures intended to keep people safe were instead becoming threats to their health in a variety of ways. Bad lighting was causing headaches and eye irritation; noise and vibration were leading to nausea and dizziness. And all sorts of airborne contaminants were causing a host of respiratory illnesses.

Among the most insidious of those airborne pollutants are volatile organic compounds (VOCs) like formaldehyde and benzene, gaseous and sometimes odourless chemicals that were (and occasionally still are) found in everything from compressed wood to body lotion. Particulate matter — bits of residue thrown off from unvented heaters, candles, cigarettes, and other sources — was also a key offender. These pollutants can cause mild symptoms like eye and nose irritation but are also strongly associated with asthma, worsened respiratory and cardiovascular illness, low birth weight, and several types of cancer. And they were all over the buildings that were making so many people sick.

It wasn’t just the buildings’ and furnishings’ byproducts making inhabitants ill. If people became sick in one of these sealed-up buildings, the airborne pathogens they spewed could linger, spreading respiratory infections. When HVAC systems didn’t adequately clean the air or the airflow in a building wasn’t carefully managed, disease-causing moulds, bacteria, and viruses could spread not only from buildings to people, but from people to people. Under the right conditions, certain building features could intensify the transmission of disease.

The worst offences against many of our senses are relatively easy to detect: Most people can tell when lighting is bad or when a building’s bowels groan too loudly. But our capacity for sensing bad air is less finely tuned. “We might notice the rancid or stale smell of mold, but there’s a lot we can’t detect”. We certainly can tell when the air is too hot or too cold for our liking.

But we’re much less likely to notice the air we’re breathing has high levels of carbon dioxide — indicating we’re breathing a lot of other people’s expelled air — or contains dangerous VOCs. When we get headaches after a day in a stuffy conference room or a nagging cough that starts a few minutes after we walk into the building, how often do we wonder if the problem is in the air?

Our sense of smell is only good for detecting indoor air quality on the really extreme end of bad, said Ian Cull, a Chicago-based environmental engineer who specializes in indoor air quality. We might notice the rancid or stale smell of mold, but there’s a lot we can’t detect. “We can probably, with our nose, tell the D minuses and the F’s,” he said, “but from an A plus to a C minus, you don’t really know.”

In the 1990s, a wave of lawsuits holding architects and engineers liable for health problems related to poorly built or maintained buildings led to massive overhauls of construction codes. The new codes created restrictions for the materials architects and engineers could use in buildings and HVAC systems. “Buildings were afraid of litigation,” said Sachin Anand, an engineer who leads a Chicago-based sustainable building firm. So most of them made meaningful changes that ultimately led to much healthier indoor climates.

By the early 2000s, complaints of sick building syndrome — and concerns about indoor air quality more broadly — had faded from the public eye.

Health problems related to bad indoor air still existed — it was just hard to prove in any individual’s case that their built environment, and not some other factor, led to a particular illness. Research accumulated linking indoor air pollution to worse cardiovascular disease; cognitive decline in older adults; higher rates of chronic respiratory diseases, lung infections, and cancers; and infectious diseases including measles, tuberculosis, chickenpox, influenza, and SARS. In schools, high levels of multiple pollutants and carbon dioxide were tied to lower academic and cognitive performance and worsened respiratory health for students.

Still, there were no national requirements to improve building designs that force hundreds of people to share the same air space. Huge numbers of students, office workers, nursing home residents, and apartment dwellers were stuck regularly breathing poor-quality air. It wasn’t clear exactly how many were breathing bad indoor air because there was no broadly accepted definition of “regularly” and “poor-quality.” (This is still true today.) And while people complained about how annoying and paradoxically antisocial designs like open-concept offices are, they rarely protested the health risks of these kinds of layouts.

This was the state of things when Covid-19 arrived. The virus exploded, and almost instantly showed itself to be particularly good at infecting people in indoor spaces with poor ventilation and poor air filtration — like in many open offices, classrooms, and restaurants.

It took much longer than it should have for health authorities to publicly acknowledge that aerosols — tiny flecks of fluid, like those created when people cough or sneeze — could transmit SARS-CoV-2, the virus that causes Covid-19, through the air. But scientists were quicker to the draw, and the public’s awareness of the new dangers of sharing airspace changed overnight.

“We’re in a place where people know that indoor air quality is important, but they’re just uncertain as to what to do,” said Cull.

“Covid was a big wake-up call”

Brett Singer, an environmental scientist and indoor air quality expert at the Lawrence Berkeley National Laboratory in Berkeley, California, agreed.

“Covid was a big wake-up call,” he said. “Whether it’s going to be a sustained concern that’s going to allow us to make the kind of structural and cultural changes that we need is an open question.”

Adapted from –

What is a MERV Rating?

MERV stands for “Minimum Efficiency Reporting Value”. MERV ratings on an air filter describes its efficiency as a means of reducing particles of 0.3 to 10 microns.

The higher the “MERV” rating the higher filtration efficiency at trapping smaller particles. The smaller particles are the hosts for viruses.

The data of the table below is derived from a test method developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).

UVira IAQ Note: The standard residential HVAC filter has a MERV rating of 8. The PremierOne™ polarized media filter has a 97% multiple pass (3 air changes per hour) efficiency at .3 microns or a MERV rating of 16.

UVira IAQ Note: Our HEPA whole house air cleaner has a 99.997% efficiency (3 air changes per hour) at .3 microns or a MERV rating of 16.

MERV Rating

Average Particle Size Efficiency in Microns


     3.0 – 10.0 less than 20%


     3.0 – 10.0  49.9%


     3.0 – 10.0  84.9%


     1.0 – 3.0 50% – 64.9%, 3.0 – 10.0  85% or greater


     1.0 – 3.0 80% – 89.9%, 3.0 – 10.0  90% or greater


      0.3 – 1.0 75% – 84%, 1.0 – 3.0  90% or greater


      0.3 – 1.0  75% or greater

COVID-19 Safety Precautions at Uvira IAQ

We are grateful that our valued customers invite us into their homes and businesses.

Customers and Uvira’s team members’ health and safety is our # 1 priority.

Our installers are required to wear masks when they enter and leave your home and when social distancing is not possible during the installation process.

If you want to check and see how your install is progressing, please give the installers a verbal heads up so they can put their mask on.

Is Ozone gas harmful?

Yes and No.

Ozone is an odourless, colourless gas made up of three oxygen molecules (O3) and is a natural part of the environment. It occurs both in the earth’s upper atmosphere, or stratosphere, and at ground level in the lower atmosphere, or troposphere.

When we breathe air unpolluted by human activities, we usually take in about 10 to 15 parts of ozone per billion parts of air (10-15 ppb). However, pollution from human activities has elevated levels of the ozone we breathe.

No adverse health impacts are expected when air quality is equal to or less than 50 parts of ozone per billion parts of air (50 ppb).

Levels exceeding 50 parts of ozone per billion parts of air (50+ ppb) will  begin to impact individuals with lung disease such as asthma, children and older adults.

PremierOne™  offers an odour control option which is part of the UVC germicidal lamp unit or it can be purchased as a standalone or upgrade.

Our ozone units have been tested. As you can see in the test results below the ozone produced is significantly below 1 part of ozone per billion parts of air (1 ppb) depending on the systems airflow – 375 CFM (Cubic Feet per Minute) or 2000 CFM. The greater the airflow the lower the ozone concentration.

How often should a change my P6100 polarized filter?

New Installs

When we install your  P6100 polarized filter the kit includes a replacement filter. We do this because your newly installed P6100 polarized filter will trap a lot of particulate matter that passed right through your old filter. We suggest you inspect your newly installed P6100 polarized filter about 3 weeks after the initial install and install the replacement filter.

Existing Installs

The rule of thumb is to replace your P6100 polarized filter every 3 months. However, every home or business has unique requirements which may require more frequent or less frequent replacement. The only way to determine what replacement schedule works for you is to inspect the filter from time to time and adjust your schedule to meet your unique needs.

UVira will supply you with replacement filters. They are sold in 3 packs which should last you about 9 months. Just contact and let us know what you need.

Why are your HVAC’s air air flow/fan settings important?

When you install a UVC germicidal lamp or a P6100 polarized filter or both the only way they can treat the air in your home or business is when that air is passing over the UVC germicidal lamp or through the P6100 polarized filter.

When we install a UVC germicidal lamp or a P6100 polarized filter, the default fan settings are for the UVC germicidal lamp or the P6100 polarized filter, or both, to be turned on when your blower motor is activated. This happens automatically when your HVAC system is heating or cooling your space. In the winter or summer this may be frequent enough to properly treat the air. In the spring and fall, your HVAC system may not operate frequently enough to properly treat the air.

What we have done in our own home is schedule the fan to operate, independently from heating and cooling cycles, for 15 minutes every hour (24/7/365) to circulate and treat the air. Our goal is to circulate all the air in our home at least 3 times every hour.

In an office or business setting, where there are more people congregated in a smaller space, it may be wise to have the fan circulate the air continuously or at least more frequently.

Your HVAC systems fan settings are usually a function of your thermostat. If you are not sure if your current thermostat has the necessary functionality we suggest you look up the make and model of your thermostat online or send the particulars to us at and we will do our best to advise you. Thermostats that have fan control functionality are always 5 wire models. If your thermostat is a 4 wire model you may have to upgrade.

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UVira IAQ Inc.

322 Forest Ave. North - Upper
Orillia, Ontario
L3V 3Y7

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UVira IAQ Inc.

24 Laguna Parkway, Unit 19
Brechin, Ontario
L0K 1B0

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