Not just clean…covid clean

At this point, we are overwhelmed with admonitions, information, and tutorials about how to keep ourselves, our workers, and our families safe.  We are seeing how-to videos and guidelines on proper handwashing and personal hygiene, but there is not as much information flooding our emails and social media on how to maintain sanitary workplace environments and facilities in general. 

Since the virus is novel (that is, it has never been seen before in humans so no one has developed an immunity), the information on transmission is rapidly developing.  According to the CDC and based upon what we know of similar viruses, transmission is generally thought to be mainly from person to person through exposure to infective respiratory droplets from cough and sneezes, or physical contact such as shaking hands followed by touching the mouth, nose, or eyes.  Social distancing mandates throughout the US are intended to inhibit transmission and can be a challenge in itself; however, sanitizing our homes and our routine work environments warrants additional consideration.

We must answer the following questions about the virus, transmission, cleaning and disinfecting:

How long do respiratory droplets remain in the air and what happens when they land on surfaces?

Droplet transmission refers to exposure via mouth, nose, or eyes due to the presence of microbes within aerosols from sneezing or coughing that are generally less than 5 micrometers.  These particles can be transmitted over 1 meter.  At this point, it is unknown how long airborne droplets remain airborne and viable for transmission.  While current evidence suggests a potential of three hours, typical conditions are likely less. 

When a viable virus lands on a surface, it can remain viable for a period of hours or days, depending on the surface material.  Currently, evidence suggests that the SARS-CoV-2 (COVID-19) Virus can survive on plastic and steel for up to 72 hours, on copper for four hours, and on cardboard for up to 24 hours.  However, the amount of viable virus decreases over this period and the half-life is significantly less than those times.  Consequently, it is important to develop guidance for cleaning, sanitizing, and disinfecting.  This leads to our next question. 

What’s the difference between cleaning, sanitizing and disinfecting?

  1. Cleaning refers to removal of foreign materials including visible dirt, debris, and fungi and invisible viruses, bacteria, and settled particulates.  This is generally conducted using water and detergents as well as vacuuming with a HEPA filtered unit.  The intent of cleaning is to remove the materials rather than render them nonviable.  It is viewed as the first essential step in a process that leads to sanitization/disinfection.  This approach makes additional efforts more practicable and efficient. 
  2. Sanitizing refers to the reduction of viable bacteria on a surface.  Sanitizer products must be registered with the EPA and meet a specific bacterial reduction criteria (for hard surfaces not used for food service, a sanitizer should reduce the number of germs by at least 99.9%).  NOTE that sanitizing does not necessarily clean dirty surfaces or remove germs; consequently, a clean surface should be prepared prior to sanitizing in order to be effective.  Sanitizer labels should state surfaces which it is intended for use. 
  3. Disinfection refers to killing germs to a greater degree than sanitizing.  Disinfectants are also registered with the EPA and kill 99.999% of germs on hard, non-porous surfaces or objects.  Disinfectants require a specific dwell time, defined as “the amount of time that a sanitizer or disinfectant must be in contact with the surface, and remain wet, in order to achieve the product’s advertised kill rate” to effectively kill germs (including viruses) following cleaning.  This only works on hard, nonporous surfaces.  The EPA has prepared a list of approved disinfectants for COVID-19 (

How do we clean and disinfect our homes, workplaces and facilities in general?

If an area can be vacated for a period of time, viral residue should not remain viable after 5-7 days.  Cleaning should be a baseline practice.  Guidance on cleaning versus disinfecting and how to do each in your homes, workplaces and facilities is provided by the CDC.  They continue to be the best source of information on the virus and prevention of its spread.  The CDC homepage provides categories of information on prevention and cleaning and disinfecting spaces (  From this page you can click the appropriate link on which facility you are interested in and there is a tab for how to clean and disinfect your facility. 

We also recommend visiting the Cleaning and Disinfecting for Households page:( ).  The background information on this page discusses ventilation of rooms and system designs which are important aspects to consider. 

Perhaps the best method to treat high contact areas (those areas that are subject to routine, necessary contact by multiple people such as counters, handles and doorknobs, keyboards, bathroom fixtures (including sink and toilet handles), copiers, etc.) is to proactively remove visible dirt or debris and wipe with a disinfecting wipe both before and after individual use.  While the required dwell time may not be met, when used in conjunction with standard hygiene practices such as handwashing, covering coughs and sneezes, and self-isolating, using a disinfecting wipe will serve to reduce potential surface biological loads. 

What do we do ourselves versus having a contractor perform? 

Individual liability, comfort level, and internal resources will guide your company’s answer to this question.  If workers are being tasked with ongoing cleanup work, they should be trained on the individual chemicals being used and the Safety Data Sheet (SDS) documentation should be maintained by the company.  Additionally, different measures may be deployed or prudent dependent on the following: 

  • If exposure to a confirmed case of COVID19 is not suspected; 
  • If a suspected case (person of interest) is present; 
  • If a confirmed case is identified.

How do we know what is clean and what is disinfected?

Testing surfaces to confirm adequate disinfection is possible.  There are specific test methods and analytical processes that target COVID-19; the turnaround time for these tests is currently 5-7 days; however, as the demand for such analyses increases, the turnaround times are expected to increase as well. 

Testing for ATP, a marker of biological activity that does not occur in viruses, may be used as a “white glove test” surrogate for evaluating cleanliness as a general measurement of biological contamination; however, it is not appropriate as a definitive confirmation for the absence of COVID-19 because it is possible that viral residue remains even if ATP has been adequately removed.  It is reasonable to conclude that the absence of ATP indicates cleaning sufficient to have significantly reduced the presence of viral contamination, particularly in the case where the cleaning was followed by disinfection and was conducted with an antiviral product specifically registered for use against coronavirus.

About the Authors

Glenn Hargrove and Jesse Phillips currently serve as the Practice Leaders for F&R’s Industrial Hygiene Group. Both maintain close familiarity with the rapidly developing science and best practices related to SARS-CoV-2 (COVID-19) coronavirus and have vast experience with assessments for a wide range of microbiological agents including mold, bacteria, and viruses. You can find more information on F&R’s COVID related and other environmental services here.