Cleaning, Sanitizing, and Disinfecting
This article is part of a series of articles designed to provide science-based information to regular people so that they can better understand the science around the COVID-19 pandemic. If this is your first time here, you may want to start at the beginning.
Looking for the answer to a specific question?
Find answers to The Big Questions at the bottom of the page.
We know that the primary way that the SARS-CoV-2 virus (and thus COVID-19 ) is spread is through aerosol droplets. When the pandemic began, and science didn’t truly understand the virus, the disease, or the modes of transmission, precautions were taken to cover all possible modes of transmission, and a lot of focus was placed on surfaces as a vector that was easier to control. Sanitizing wipes became almost impossible to find, and any product in the store that claimed it killed 99.9% of anything flew off the shelves.
People used many terms to describe how to halt the spread: cleaning, sanitizing, disinfecting. Some people viewed these terms as interchangeable, but each has a specific meaning, and there are specific reasons to choose each one. What do the words actually mean? What is the difference between cleaning, sanitizing, and disinfecting?
When a product says it kills 99.99% of germs, what does that mean? Do you need to follow certain precautions for the products to work properly? And do you need to purchase specific products to kill germs and viruses, or do some of the products you already have at home do the job?
A note about ‘killing’ viruses: As we discuss in Part 1: What Is A Virus, viruses are not really alive. So while the term ‘kill’ may be used in reference to viruses, disinfectants really inactivate the virus so they cannot cause harm.
Fomites & Fomite Transmission
There are many different forms of disease transmission. By now, we’re all likely familiar with aerosol transmission – when a pathogen contained in aerosol droplets passes from one animal to another, or Vector-borne, where a disease is spread by an insect (such as malaria or Lyme disease). Fomite Transmission is the name for when a pathogen is transmitted by an inanimate object, or “fomite”. A fomite is any inanimate object, such as a doorknob, light switch, or cell phone, that a pathogen can remain on and be passed from person to person. Fomite transmission can include secondary sources of exposure – for example, when a pathogen is transferred from an elevator button to a finger, and then the finger is used to rub your eye (or pick your nose!).
Imagine a freshly painted wall. Unknowingly, you place your hand on the wall, covering the surface of your hand with paint. You then open a door and leave paint behind on the doorknob. The next person who opens the door also gets paint on their hand and they might place their hand on another wall. Each time the paint moves to a new surface less paint is deposited, but the paint is still present.
Note: The idea of cross-contamination of disease is a common form of Obsessive-Compulsive Disorder called Contamination OCD. While you should make every effort to be safe, such as washing your hands, if the fear of germs or disease is causing stress in your life, consider talking about it with a medical professional.
In order to remove pathogens and other contaminants from surfaces that we interact with every day, there are three commonly discussed methods.
What Is The Difference Between Cleaning, Sanitizing, And Disinfecting?
Cleaning removes dirt, oils, dust, and germs from surfaces. Cleaning generally involves using soap and water and mechanical action (such as scrubbing or high pressure) to remove objects from those surfaces. Cleaning may remove some pathogens, and soap may even kill some pathogens leaving behind fewer pathogens that can cause infection.
Sanitizing is defined by Health Canada as reducing the population of microorganisms on environmental inanimate surfaces and objects. Sanitizing may still leave microorganisms on surfaces. In the United States, the CDC defines sanitizing as “removing the number of bacterial contaminants to safe levels as judged by public health requirements”. Today, many people will think of hand sanitizer when they think of sanitizing, but “surface sanitizers are considered pest control products and must be registered before they can be manufactured, imported, distributed, sold, or used in Canada to ensure they meet Canadian health and environmental standards.“ Surface sanitizers are NOT as effective as disinfectants but may be suitable for your use.
In Canada, disinfectants are treated like drugs and all disinfectants that are approved for sale in Canada will have a drug identification number or DIN. Most disinfectants will likely work against SARS-CoV-2, the virus that causes COVID-19, but Health Canada records disinfectants that have demonstrated that they are effective specifically against SARS-CoV-2 and maintains a list of these hard surface disinfectants on their website.
Disinfectants, household cleaners, and bleach are meant to be used to clean surfaces. Never use these products on the skin or internally (e.g. by swallowing or injecting these products) as this could cause serious harm. – Health Canada
Contact Time or ‘Kill Time’
True disinfectants are not just cleaning products, they are actually tested and controlled by Health Canada as a drug, and are issued a Drug Identification Number. The process of being tested by Health Canada ensures that each product actually does what it claims when the proper instructions are followed. One important part of these instructions is ensuring that the appropriate Contact Time (sometimes referred to as ‘Kill Time’ or ‘Wet Time’) is observed.
Contact Time is the length of time that a surface or object must remain wet with the disinfectant for the disinfectant to work properly and kill all of the germs. Different products have different amounts of Contact Time. This time will be included on the spec sheet for the product along with other information such as pH, and whether or not the product is Food Safe or needs to be rinsed after application.
Contact Time will vary depending on the concentration and strength of the disinfectant being used with stronger and more concentrated chemicals having a shorter Contact time.
Based on this, it might seem to make sense to choose a disinfectant with the highest concentration of active ingredients, but there is a cost. Having a higher concentration and stronger solution may reduce the time needed to disinfect a hard surface, but it also often means that the disinfectant is more likely to leave behind more residue and eventually cause damage to the surfaces which are being cleaned repeatedly.
How Do Disinfectants Work And What Kinds Of Disinfectants Are There?
Disinfectants can be made from many different types of compounds, including Alcohol, Chlorine, Hydrogen Peroxide, Quaternary Ammonium Compounds, and many more. Choosing the proper disinfectant for a specific use case is a subject of much research as the end-user must consider the surfaces to be disinfected, temperature, humidity, ease of use, Contact Time, and whether the disinfectant is food safe.
Different types of disinfectants work in different ways. For example, acidic disinfectants destroy the bonds of nucleic acids and precipitating proteins, while phenols denature proteins and inactivate membrane-bound enzymes.
Food Safe or Food Contact Surface disinfectants are those that can be used in settings where food may come into contact with the surfaces being disinfected, such as restaurants or movie theatres.
How to Properly Disinfect A Hard Surface
Remove Debris. Remove debris from the surface. Imagine trying to spray disinfectant on a surface that was covered in breadcrumbs. The disinfectant may not be able to get under the breadcrumbs, leaving those spaces not disinfected. By removing debris (including dirt, garbage, or food) we ensure that the disinfectant will have full access to the surface to do the work.
Cleaning. Using warm soapy water, wash and dry the surface prior to disinfecting. Washing with soapy water will remove dirt and oils from the surface to allow the disinfectant to have complete access to the surface. Ideally, let the surface air dry or dry with a towel.
Disinfect. Following the instructions on the container, allow the disinfectant to sit on the surface for the specified Contact Time.
Never mix cleaning or disinfecting products. For example, if ammonia and bleach come into contact with each other they create chloramine gas which is toxic to people and animals.
The Big Questions
Does COVID-19 spread on surfaces?
“SARS-CoV-2, the virus that causes COVID-19 may be spread when a person touches another person, or a surface or object that has the virus on it, and then touches their mouth, nose, or eyes with unwashed hands.” - HEALTH CANADA
Can I catch COVID-19 from doorknobs or other surfaces?
“Viable SARS-CoV-2 virus and/or RNA can be found on surfaces for periods ranging from hours to days. Despite consistent evidence as to SARS-CoV-2 contamination of surfaces and the survival of the virus on certain surfaces, there are no specific reports which have directly demonstrated fomite transmission. However, fomite transmission is considered a likely mode of transmission for SARS-CoV-2, given consistent findings about environmental contamination in the vicinity of infected cases and the fact that other coronaviruses and respiratory viruses can transmit this way.” - WORLD HEALTH ORGANIZATION
Do I need to wash my groceries?
“Wash fruits and vegetables under running water. Washing fresh produce with soap, chlorine, or other chemicals is not recommended.” - HEALTH CANADA
“There is no evidence to date of viruses that cause respiratory illnesses being transmitted via food or food packaging.” - WORLD HEALTH ORGANIZATION
What can I use to disinfect my home?
“In non-healthcare settings, sodium hypochlorite (bleach/chlorine) may be used at a recommended concentration of 0.1% or 1,000ppm (1 part of 5% strength household bleach to 49 parts of water). Surfaces must be cleaned with water and soap or a detergent first to remove dirt, followed by disinfection.” - WORLD HEALTH ORGANIZATION
“Prepare a diluted bleach solution according to instructions on the label or if using bleach that has a concentration of 5% hypochlorite, add 5 mL (1 teaspoon) of bleach in 250 mL (a cup) of water, or add 20 mL (4 teaspoons) bleach in 1 litre (4 cups) of water to give a 0.1% sodium hypochlorite solution. Be sure to prepare the solution fresh, when you are intending to use it, and only dilute bleach in water (and not with additional chemicals).” - HEALTH CANADA
Do you need to disinfect? Learn about the difference between cleaning, sanitizing, and disinfecting (above). Many cleaners, sanitizers, and disinfectants are available for home use - read and follow the labels and instructions carefully. Do not mix different types of cleaners.
What are the best ways to prevent me and my loved ones from getting COVID-19?
Follow all Public Health Orders.
Get vaccinated as soon as you are able to.
Stay at least 2 meters away from others who do not live in your household.
Avoid crowds and poorly ventilated spaces.
Clean and disinfect frequently touched surfaces.