Show Me The Science: The Impact of Floors on Indoor Air Quality & Health

Categories: Cleaning Best Practices, Cleaning for Health & Safety, Innovations, Trends & Technology

By Jeff Cross | May 31, 2022 << Back to Articles Show Me The Science: The Impact of Floors on Indoor Air Quality & Health

Cleaning for appearance is what drives virtually all cleaning professionals and technicians, whether in facilities, for building service contracting companies, or professional floor cleaning companies.

Yet we all know that cleaning for health, whether surface cleaning or improving indoor air quality, is critical, and the science is emerging now more than ever before. The world has changed, and more people are demanding proof that the homes and buildings they inhabit and use are clean and safe. It’s a demand that we should embrace, because it involved the work we do and the impact the cleaning industry has on better health.

With this in mind, I sat down with two industry professionals: Doug Hoffman, the executive director of the National Organization of Remediators and Mold Inspectors™  (NORMI), and Dr. Gavin Macgregor-Skinner, a senior director with the Global Biorisk Advisory Council® (GBAC), a Division of ISSA. Both have a passion for cleaning beyond appearance. In other words, cleaning for health, and by doing that, protecting people in buildings by using science as a guide.

Concerned about your facility’s IAQ? Attend the inaugural GBAC Symposium on Air Considerations. Learn more and register today!

The following Q&A feature article should be used by all cleaning professionals as guidance and justification for the work they do.

Q: What do we know and not know about contaminants on floors?

Doug Hoffman, the executive director of NORMI

The floor is the largest horizontal surface in any building and, therefore, a repository for all types of contaminants. We know about the breadcrumbs, dog hair, and mud from our shoes, but have we considered the microscopic stuff that has been floating around in the air and now settled out on the floor? There’s plenty of it. The microbes and mold spores for potential mold growth?

Cracks and crevices are enemies when it comes to keeping floors clean, and luxury plank flooring, wood, floor tile, and even sheet vinyl are full of them. And then there is the carpet, the largest filter in the building, collecting whatever falls on the floor and trapping it in the fibers and padding. It is seldom noticed, but if you have ever pulled up carpet to replace it, you know the incredible amount of dirt and grime that can collect underneath our feet.

Some areas of the building are dirtier than others because of the higher volume of traffic, and the floors show it. Moisture-prone areas like bathrooms and laundry rooms soak up spills and create a haven for bio-nesting for mold and bacteria.

Dr. Gavin Macgregor-Skinner, a senior director of GBAC

The U.S. Centers for Disease Control and Prevention (CDC) published guidelines on Cleaning and Disinfecting Your Facility: Every Day and When Someone is Sick (updated November 15, 2021) that were for cleaning and disinfecting buildings in community settings to reduce the risk of COVID-19 spreading. The guidance lists examples of high-touch surfaces such as pens, counters, shopping carts, tables, doorknobs, light switches, handles, stair rails, elevator buttons, desks, keyboards, phones, toilets, faucets, and sinks.

But there’s been very little discussion or guidance provided on the risk of floors in spreading SARS-CoV-2 virus that causes COVID-19 disease or even the spread of infectious disease-causing agents (virus, bacteria, fungus) on your shoes.

Other published government guidelines for COVID-19 and other infectious diseases similarly provide very little on cleaning and disinfecting floors.

Here are some issues affecting floors in the spread of infectious diseases:

  • Step 1: Infected person coughs or sneezes, producing respiratory droplets that contain bacteria or viruses that land on surfaces in their location.
  • Step 2: Bacteria or virus is now transferred onto various surfaces, including the floor.
  • Step 3: Person walks on the floor, and bacteria or virus is now transferred onto their shoes. Risk of virus spreads as they walk around from the soles of shoes or aerosolizing back into the air.
  • Step 4: Person returns home, further spreading the virus.
  • Step 5: Person takes off their shoes. Bacteria or virus has now transferred onto their hands.
  • Step 6: Person, not knowing the virus is on their hands, touches their face, increasing the likelihood they become infected.

As the largest horizontal surface in a building, the floor is a breeding ground for all types of germs and contaminants. Appropriate cleaning, sanitizing, and disinfecting guidelines and regular floor maintenance are key components to successful infection-risk mitigation.

When people enter a building, unless they can visibly see a dirty floor, they may not think about the floors as a source of germs that can make them sick. But there is research that shows floors are covered with germs that can be a potential source of infection.

Even if we don’t directly touch the floors, most of us don’t consider what may be on our shoes or socks. We most likely do not think to wash our hands with soap and water every time we put on or remove our shoes.

By washing your hands and minimizing your interaction with floors, you can decrease your risk of infection and the risk of spreading infection to others.

We need to be better educated on which germs can survive on floors and how they spread.

A study published by Deshpande and colleagues in the American Journal of Infection Control focused on what bacteria might live on floors of hospitals. The researchers used swabs and then cultured the samples from 120 floor sites among four Cleveland-area hospitals. The bacteria they found that could lead to hospital-acquired infections included:

  • 22% of the floor sites were positive for methicillin-resistant Staphylococcus aureus (MRSA), which can cause skin infections, bloodstream infections, and pneumonia and is resistant to many common antibiotics.
  • 33% of the floor sites were positive for vancomycin-resistant enterococci (VRE), which can cause urinary tract infections and wound infections, a real concern. And in addition, it is resistant to vancomycin, an important antibiotic.
  • 72% of floor sites were positive for Clostridium difficile (C. diff), which causes severe diarrhea. This study found that C. difficile was not only found on floors in isolation rooms where people with this infection are kept but also in other rooms where people did not have this infection. This shows that C. difficile is able to spread between rooms and can survive on floors.
  • 24% of high-touch objects that were in contact with the floor were contaminated with more than one bacterium.
  • 57% of contaminated objects in contact with the floor transferred bacteria to hands.

Q: What is the correlation between surfaces, such as floors and indoor air quality? What type of testing can prove what you believe?


When performed by a well-trained professional, the IAQ assessment always includes testing both surfaces and air for contaminants. We may not think about how our surfaces get so dirty, but much of the surface contamination we collect from surface samples is the result of airborne contaminants settling out. The dust we see on our piano is dust that has been in the air, and now, through natural ionization processes, becomes the haze that needs to be wiped from the surface. Dead skin cells, mold spores, pollen, insect parts, and pet dander are some of those airborne contaminants that eventually land on the surfaces of our bookcases, furniture, and floors.

Microbes do not have wings but do have the tendency to float around on the small particulate like a magic carpet ride. We may inhale them or touch a surface where they have landed, and suddenly we now have what someone else had, and we did not even have contact with that person. Additionally, touch transmission is another reason why it is important to keep all our surfaces clean, including our floors.

Diagnostic testing is objective and can show us exactly how contaminated our surfaces are and, after cleaning, can prove we have done a good job removing the contamination that was in the air and is now on the ground. Swab sampling, bulk sampling, swipe, and carpet sample collections are great options to evaluate what’s going on with our floor surfaces.

Q: What do you recommend we do about these contaminants and cleaning processes for floors? How can we really make a difference for building occupants?


The challenges we face in a post-pandemic society are not new, but now is the appropriate time for all industries to rethink and reassess their approach to infection-risk mitigation. Choosing appropriate flooring materials and ensuring that standard operating procedures for cleaning, sanitizing, and disinfecting floors are adhered to will make a crucial difference in maintaining a healthy workforce and protecting the public.

It is important that cleaning floors for infection prevention isn’t overlooked. We can improve this through education and sharing studies that show that infectious disease pathogens can easily spread via foot traffic and floors, not just by person-to-person contact or droplets in the air.

Studies show that floors and shoe soles can have high concentrations of bacteria and viruses and be tracked to other rooms. The presence of germs on floors is largely attributed to gravity and airflow, but then they can be carried elsewhere by foot traffic or can re-enter the air from the ground due to foot traffic. As people walk, they not only collect and spread germs on the soles of their shoes as they move from one area to another but this can also aerosolize bacteria or viruses when they kick them back in the air.

This further illustrates the need for regular and thorough cleaning and disinfecting of all floor surfaces, in addition to the high-touch surfaces, which often receive the greater focus for disinfection.


Objective methods of testing surfaces, like surface sampling, could allow us to compare post-cleaning sampling to a pre-cleaning baseline, helping us evaluate the cleanliness of the surfaces under our feet. But this, unfortunately, is seldom done and most often discouraged. We recommend objective testing in every assessment.

Carpeting is especially difficult to keep clean but should be vacuumed regularly to reduce the collection of contaminants. You have probably seen videos where vacuuming itself creates a dust cloud that only settles back into the carpet once the vacuum is turned off. That only confirms that regular daily vacuuming needs to be done. A good maintenance schedule should include carpet cleaning techniques that are thorough but protect the carpet.

When cracks and crevices are apparent in wood, luxury plank, or vinyl tile, special care should be taken to periodically scrub the surfaces with a soft bristle brush rather than relying only on the occasional dust mop. Pushing around the dust often allows it to fill those cracks and create an opportunity for mold to grow if a spill should occur.

Tile grout is a sponge that absorbs moisture, so care should be taken to seal the grout. By filling the surface with suitable sealant, and applying it on a routine basis, there is less possibility of trapping contaminants, and the surface will become smoother and easier to keep clean.

We do not think about the fact that things in the air land on the surfaces, and things on the surfaces become airborne.

Q: Why are not more resources spent on removing contaminants and cleaning for health? What surprises you the most?


This is a good question, and I do not know if I have a good answer. I remember when I was in the building trades and I wanted to do something that I knew would build a better house, the response was usually, “Yes, that would be nice, but I’d rather have granite countertops.” It seems like the idea of cleaning for appearance instead of cleaning for health has become a way of life. We need to address this.

It might be that resources are not dedicated to this, and budgets are slashed because we are more concerned about what people can see than about what they cannot see, and yet what they cannot see is the most dangerous.

Scientists tell us that the most hazardous particulate in the air is not the stuff trapped in a filter but the submicron particles that go right past our nose hairs and get lodged deep in our lungs. There’s evidence that some of that tiny stuff can enter our bloodstream, the stuff we can’t even see with the naked eye. Waterborne illnesses often come from “clear” water because no one would drink cloudy water. We cannot see these contaminants, but those are the ones that are most dangerous. Therefore, it is so important to incorporate testing into any cleaning protocols.


Koganti and colleagues conducted a study to determine the extent that germs from the floor spread to the hands of people, as well as high-touch surfaces, both inside and outside the hospital room. They took bacteriophage M2, a nonpathogenic virus engineered not to cause infection, and placed it on wood laminate floors next to hospital beds.

They then swabbed a variety of surfaces to ascertain if and where the virus had spread. It was reported that the virus had spread to not only hands, shoes, and socks, but also bed rails, bed linens, tray tables, chairs, pulse oximeters, doorknobs, light switches, sinks, and even close-by rooms and nursing stations. In the nursing station, the virus was found on the keyboards, computer mice, and phones.

This study showed that infectious disease-causing pathogens on hospital floors could spread to many surfaces both inside and outside the hospital room.

Q: If you could build a team to keep buildings healthy, what would that look like, especially with floor care?


If I were building a cleaning team to keep buildings healthy, I would do personality profiling to find detail-oriented people. I would look for people who are obviously concerned about their appearance and who keep their cars clean. Seriously, I have found it difficult to teach someone who is untidy to be as concerned about the cleanliness of surfaces as I am. I would want them to buy-into a rigorous cleaning schedule and enjoy the challenge of keeping it clean.

My mother thoroughly cleaned our house every spring and fall, which would include pulling all the rugs out of the house, cleaning the Venetian blinds (I got that job), and washing the windows inside and out. That seems to have become a lost art, and most cleaning now is for appearance, not for health.

I would build a team that understands that appearance is NOT as important as health, because if you are cleaning for health, the appearance will take care of itself. Cleaning cannot be a low-budget item and requires ongoing toolbox training to keep the team sharp and current on new chemistries and techniques.

Q: How do we convince those we clean for and who oversee cleaning budgets to increase the frequency and quality of cleaning?


We need to define what “clean” is, and we need to measure it. With respect to floors, both detergents and disinfectants help to control germs. But they are not synonymous. Detergents remove dirt, grease, and germs through scrubbing with soap and water solutions. Disinfectants are chemical or physical interventions requiring dwell time or contact time to kill bacteria and inactivate viruses.

We need to ensure our cleaning methods target the right sites for decreasing the risk of infection and are applied frequently enough to reduce the number of germs that could cause infection.


COVID-19 brought a heightened awareness to the table. But, like so many things, I fear we are becoming distracted, and maybe laxer, about the frequency and quality of our cleaning processes. We should be talking more about the contaminants that we live with every day, not just the latest virus variant. If we realized how we could reduce illness and increase the quality of our health by simple, regular, and thorough cleaning of all surfaces, we would be encouraged to do better.

We have tremendous new technologies in air filtration/purification equipment that reduce the airborne contaminants and keep surfaces, including floors, cleaner. We should incorporate these in every way we can. We have ways of monitoring indoor air quality to catch anomalies before they become a problem and provide ongoing sampling to verify that our cleaning processes are working. This kind of holistic approach is the answer and educating the decision-makers on the long-term benefits of such will convince them of the importance of this line item.

Q: Who is responsible for protecting public health when it comes to indoor spaces?


As much as I would like to think that someone else is responsible, I am convinced that, like so many things, it is up to me. The building owner, property manager, facilities maintenance director, or leasing company certainly must bear some responsibility for the cleanliness of their buildings. Still, I believe, and have experienced, the truism that “the squeaky wheel gets the grease,” so I need to become that “squeaky wheel.” This does not have to be a confrontation but a simple sit-down to discuss my needs and concerns about my own health and the health of my family or workers. If the millennial employee has taught us anything, we have learned that the needs of the individual must have a seat at the table, so expressing our needs is a great place to start.


It is everyone’s responsibility. Cleaning for health needs to be part of a business’s continuity of operations plan. But we know all too well, that when a facility needs to cut costs, cleaning is a cost-cutting target.

CEOs and senior management need to understand that removing visible and invisible dirt from floors and surfaces in their buildings requires trained staff, ongoing monitoring, measurement of bioburden, education, continuous improvement processes, and two-way communication between those responsible for cleaning and the users of the building, as well as those responsible for budget, health, and safety.

Q: If you were to give a short speech to cleaning professionals, what would you tell them?


Cleaning of floors and other surfaces that accumulate infectious disease-causing agents was often a low priority. Times have changed. We know surfaces serve as a source of infection. As a cleaning professional, you need to learn the science and the evidence-based procedures and go to market with “Cleaning for Health.”


You are the front-line first responders dealing with indoor environmental contamination. You are the one who can improve the health of those you serve. You can protect them from whatever danger they might face, from touching contaminated surfaces to breathing contaminated air. You must be sure they return home in the same condition which they came to work. And by taking good care of the air and the surfaces, you will be protecting your own family when you return home after a hard day of work of keeping the building clean. It is that important.

There are very few things in our indoor air environments as dynamic as indoor air quality and the condition of our surfaces. It is constantly changing. The possibility of a life-threatening or debilitating illness is ever present and needs to be continuously addressed. But the good news is this: Getting a grip on the correct procedures and processes that manage the quality of cleaning produces a much cleaner, safer, and healthier environment.

IAQ management is about controlling the quality of the air we breathe and the cleanliness of the surfaces we touch and walk on. On a personal note, I have great faith that people really want to do the right thing and do a good job. When properly educated and trained, they will rise to the occasion and make things better. 


CDC Guidelines on Cleaning Your Facility: Every Day when Someone is Sick (updated November 15, 2021)

Deshpande, A., Cadnum, J.L., Fertelli, D., Sitzlar, B., Thota, P., Mana, T.S., Jencson, A., Alhmidi, H., Koganti, S., Donskey, C.J. (2017). Are hospital floors an underappreciated reservoir for transmission of health care-associated pathogens? American Journal of Infection Control, 45, 336-338.

Guo, Z., Wang, Z., Zhang, S., Li, X., Li, L., Li, C….Chen, W. (2020). Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020. Emerging Infectious Diseases, 26(7), 1583-1591.

Koganti S, Alhmidi H, Tomas ME, Cadnum JL, Jencson A, Donskey CJ. Evaluation of Hospital Floors as a Potential Source of Pathogen Dissemination Using a Nonpathogenic Virus as a Surrogate Marker. Infection Control & Hospital Epidemiology. 2016 Nov;37(11):1374-1377.

About the Author.

Jeff Cross is the ISSA media director, with media brands that include ISSA Today, Cleaning & Maintenance Management, and Cleanfax. He can be reached at [email protected] or 740-973-4236.