Tips for mitigating influenza in commercial buildings

With cold and flu season upon us, spending time reviewing your HVAC system, its major components as well as air and water distribution is time well spent to help mitigate the spread of type A (H1N1) and other types of Influenza. Some of the precautions may be based in adopting simple common sense measures while others are related to proper maintenance protocols. In addition, there are system upgrades that can be performed to further mitigate risks. Below is a list of tips to consider during cold and flu season:


  • Monitor facilities to ensure that no warm, stagnant water is present as it can provide an environment conducive to the growth of problematic microbes such as Legionella, the cause of Legionnaire’s Disease.
  • Monitor areas including cooling towers, pooled water on roofs or clogged drains that can harbour unhealthy contaminants that can be introduced into the building and circulated by the air distribution systems into the occupied spaces
  • One simple upgrade facilities can implement is to upgrade the efficiency of the air filters.  As filter efficiency increases, typically their resistance to air flow also increases.  Always check to be sure the fan system can handle the resistance being imposed by the filters and other components in the system.  Also, select replacement filters based on the specific particles you intend to collect.  Viral droplets or droplet nuclei of influenza for instance are very small but are typically surrounded by a mucus shell making them larger and easier to remove.
  • It is necessary to re-evaluate how and when filters should be changed.  Rather than via a simple schedule, it may be more prudent to measure the pressure drop through filter banks and set up basic performance metrics to determine the best model for filter changes.
  • Simple measures are the first line of defence.  Technicians should wear cut-resistant gloves when performing filter changes or basic maintenance to air dampers and commonly exposed system components.  Also, properly fit respirators to ensure that the risk of exposure while working above the ceiling or in poorly ventilated areas is minimized.
  • A common service and maintenance procedure is to verify correct outside air intake dampers settings and operation.  Trane recommends that most commercial spaces operate at a slightly positive pressure relative to the outdoors to reduce the likelihood of contaminants infiltrating into the occupied areas.
  • Check and validate restroom and other critical area exhaust fans to assure that they are removing contaminants from the building before they become mixed with the indoor air.  Perform preventive maintenance on small exhaust fans to ensure they have not accumulated dirt, reducing their effectiveness.
  • Provide staff with basic training and increase overall awareness about the risks of influenza exposure and the likely ways to contract the virus.  Also, conduct formal training of staff technicians and subcontract workers in how to work with your building systems to reduce risk and increase health and safety as well as reducing exposure to other harmful airborne particles.
  • Direct contact is the most common pathway for the spread of disease.  Communicate influenza safety tips and precautions to all building departments – especially those whose primary function includes occupancy of guests, visitors and the general public.
  • Encourage hand washing among all staff.  If possible, add hand cleaner and hand sanitizer supplies at air handler locations, equipment controls, railings and access doors.

Additional Resources

There are many resources to provide details and more complete planning recommendations. Although written by American institutions, they are still helpful and include: 

·        IFMA Foundation’s Pandemic Preparedness Ma
nual (

·        The Center for Disease Control and Prevention (

·        The Federal Emergency Management Agency (

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