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Ventilation Helps Reduce Flu Transmission

ventilation poster

The days are getting shorter and the temperature is dropping.  As an added bonus, we have flu season to contend with. Every year we are encouraged by medical professionals to get a flu shot and take basic precautions like basic hand hygiene and avoiding close contact with sick individuals.  Let’s add another weapon in your arsenal to protect yourself against the flu by improving the ventilation of your home.

What is the Flu?

First, it is important to distinguish the flu from the common cold.  Both illnesses share very similar symptoms, however, the flu tends to be more severe.  It typically comes on quickly and severely whereas the common cold does not. Some people describe the flu as “being hit by a truck.”  Each illness can also be distinguished by the type of virus. The flu is caused by the influenza virus and the common cold can be caused by many types of viruses.  To determine if you have the influenza virus, a doctor may run a rapid influenza diagnostic test which looks for special markers on cells – these are called antigens – to determine if the virus that is making you sick is indeed influenza.  

Does Ventilation Help Reduce Transmission?

According to the Centers for Disease Control, people can spread the flu to others who are 6 feet away 1.  Influenza is spread through droplets from infected people when they sneeze, talk, or cough. These droplets are carried by air.  Several studies have been conducted to determine if the ventilation of a space can affect the transmission of influenza and other infectious diseases.  Ventilation refers to the amount of outdoor air that is supplied into a building. Many studies found that there is “strong and sufficient evidence to demonstrate the association between ventilation and the control of airflow directions in buildings and the transmission and spread of infectious diseases” 2.  One study sampled the filters in an office building for the presence of the rhinovirus, which does not cause the flu but it does cause the common cold. The researchers also collected samples from building occupants with upper respiratory infections. These samples were collected at different time intervals while the amount of the outdoor air supply was changed.  The results suggested that “occupants in buildings with low outdoor air supply may have an increased risk of exposure to infectious droplet nuclei emanating from a fellow building occupant” 3.

How do you ventilate?

The easiest and cheapest way up front to ventilate a space is to open a window or door.  This is known as natural ventilation. In the winter months when the flu season is in full effect, it is not very practical to have windows open.  A way to increase the ventilation in a home without compromising security and thermal comfort is to have an outdoor air intake tied to the HVAC system.  This would introduce fresh air into your home mechanically versus naturally. Another option would be to install an energy recovery ventilator (ERV) or a heat recovery ventilator (HRV).  These systems recover energy that would normally be exhausted and reintroduce it back into the home along with fresh air. Although you must purchase and install these units, they save on heating and cooling costs.


Although the flu is a common problem, there are some steps you can take to avoid getting sick.  Increasing the ventilation in your home can help reduce the transmission of the flu. If you feel that your home is stuffy and is not getting enough fresh air, it may be worth checking the ventilation of your home.  

The picture included in this post is from 1918 encouraging people to keep their windows open to prevent the spread of the Spanish Influenza which killed a quarter of the U.S. population 4.  They had the right idea back then and it still holds up today. If you’re concerned about the ventilation of your home, feel free to contact Indoor Science to do an evaluation.

  1. Centers for Disease Control and Prevention. CDC twenty-four seven. Saving Lives, Protecting People https://www.cdc.gov/flu/about/disease/spread.htm
  2. Role of ventilation in airborne transmission of infectious agents in the built environment – a multidisciplinary systematic review Y. Li G. M. Leung J. W. Tang X. Yang C. Y. H. Chao J. Z. Lin J. W. Lu P. V. Nielsen J. Niu H. Qian A. C. Sleigh H.‐J. J. Su J. Sundell T. W. Wong P. L. Yuen First published: 25 January 2007 https://doi.org/10.1111/j.1600-0668.2006.00445.x Cited by: 233 Dr Yuguo Li Department of Mechanical Engineering The University of Hong Kong Room 7‐2, Haking Wong Building Pokfulam Road Hong Kong SAR China.
  3. Am J Respir Crit Care Med. 2004 Jun 1;169(11):1187-90. Epub 2004 Jan 30.
    Detection of airborne rhinovirus and its relation to outdoor air supply in office environments. Myatt TA1, Johnston SL, Zuo Z, Wand M, Kebadze T, Rudnick S, Milton DK. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02115-6021, USA.
  4. Photograph 165-WW-269B-22; Medical Department – Influenza Epidemic 1918 – Influenza epidemic impedes war progress. Trolley car windows were kept open to prevent the spread of Spanish Influenza which did much to slow up war progress in this country. This photo was taken in Cinc; 11/8/1918; Medical Department – Influenza Epidemic 1918; American Unofficial Collection of World War I Photographs, 1917 – 1918; Records of the War Department General and Special Staffs, Record Group 165; National Archives at College Park, College Park, MD. [Online Version, https://www.docsteach.org/documents/document/window-open-influenza-poster-trolley, October 26, 2018]

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”