Cold weather increases the risk of infection due to enclosed spaces

During winter, the air we breathe feels fresh and clean thanks to the cold. What many don’t understand, however, is temperature is not the only difference. Our hands feel drier . . . static charge builds up easily . . . our exposed mucous membranes dry out. What’s happening, and is there anything we can do to counteract it?

When the temperature outside drops, the humidity level drops along with it and the air becomes dry and arid. This, in turn, affects our body in different ways, but above all, it irritates and dries out our mucous membranes which makes us more susceptible to infections. When we sneeze, cough, sing, talk or even breathe, we exhale droplets that may contain infectious particles. Because of the dry air, the moisture in the larger droplets evaporate quickly and the now smaller, lighter droplet remains airborne for a longer period of time before eventually settling out of the air. This increases the risk of inhaling the infectious particles. 

How are particles released in the air?

Humans constantly shed particles from the skin and while exhaling. According to scientists at Lund University in Sweden, more particles are spread when we sing or scream which can be clearly seen in the video below. In order for an infected person to spread infection, the droplets containing the infectious substances such as viruses, must survive in the air long enough for a healthy person to make contact with them. Smaller droplets that contain fewer viruses can remain in the air longer and travel on air currents further while larger droplets containing significantly more viruses fall faster to nearby surfaces.

Exhaled respiratory particles during singing and talking

This video is part of a research study at Lund University in Sweden which investigates aerosol and droplet emissions during singing, as compared to talking and breathing.
Here is the source for more details:

Exhaled respiratory particles with face mask

This video is part of a research study at Lund University in Sweden which investigates aerosol and droplet emissions during singing, as compared to talking and breathing.
Here is the source for more details:

How are particles transported?

Several factors affect how particles are spread in the air. The indoor environment is crucial as ventilation plays an important role in the journey. In the case of poor ventilation or recirculated air, there is reduction in the capture of droplets and the risk of infection increases. Particles that are <5 µm are classified by many leading authorities as aerosols which means that they stay in the air longer and spread more easily. Particles that are >5 µm are called droplets. Research shows particles that are 5 micrometers fall 1mm/s and bigger, larger particles approximately 100 micrometers in size fall at 30 cm/s. Due to their greater weight, these heavier particles fall to the ground faster, about 1 mm/second. According to Jakob Löndahl, Associate Professor in Aerosol Science at Lund University in Sweden, particles and droplets up to 100 micrometers can travel a good distance in the air. When we inhale infected air at a short distance (droplet infection), it is always a mixture of large and small particles.

To get infected, the particles must reach the body, and this is what is known as airborne infection. Through the inhaled air we have a direct path down to our respiratory system and this results in infections that cause various sicknesses. Though not as common, but possible, droplets can survive for a period of time on surfaces. The risk of getting an infection is possible when we touch a surface with active viruses and bacteria, or by ingesting bacteria and viruses from our hands, and other kinds of direct contact.


How can we prevent the infection?

The combination of pollutants from both indoor and outdoor sources in the environment creates a major impact on indoor air quality. Indoor air quality can be up to 50 times more polluted. Depending on the ventilation solution, particles may remain suspended in a room and infectious particles can survive for several hours if no actions are taken to remove them from the air. External factors are difficult to influence but we can do a lot to improve our indoor environment.

A study recently published by Akademiska Sjukhuset in Sweden shows that proper ventilation is the key to reducing the spread of infection. Inactive coronavirus (non-infectious virus) has been found in air filters in the ventilation exhaust which shows that the ventilation system is doing the job properly by removing harmful pathogens from the room. If you can increase the number of air changes in the room, much progress can be made in preventing the spread of infection.

This result shows that it is important to have the appropriate number of air changes per hour so that we replace the room’s volume of air on a regular basis. To create good indoor air quality, it is also important to review your filters in the facility. We recommend that you use air filters rated MERV 15A under ASHRAE Standard 52.2 with Appendix J. Also, make sure to change the air filter at the correct intervals and undergo regular maintenance. As a complement to the ventilation, you can also install air purifiers which is also the fastest and easiest way to improve the air quality in a room. Camfil’s  City M or CC500 air purifiers reduce at least 99.99% of particles 0.3 micron or larger and are very effective in all public environments such as offices, hospitals, hotels, or hairdressers.

8 tips to prevent airborne infection
  • Keep distance
  • Wash your hands
  • Cough and sneeze in your elbow
  • Respiratory protection masks (face masks)
  • Install air purifier
  • Review your filters in the facility
  • Increase the number of air changes
  • Keep surfaces clean


Created Friday, January 15, 2021
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