Air conditioning is acceptable to use when someone has COVID-19, but specific adjustments are needed to minimize the risk of viral spread. The concern is the movement and recirculation of air, which affects how virus-laden aerosols are distributed within a shared indoor space. Informed changes to your heating, ventilation, and air conditioning (HVAC) operation can balance the need for a comfortable environment with the necessity of mitigating airborne transmission.
AC Use and Personal Symptom Management
Maintaining a stable and comfortable indoor environment is important for managing COVID-19 symptoms and supporting recovery. Air conditioning helps regulate temperature, which is beneficial if the infected individual is experiencing a fever. A comfortable room temperature can improve sleep quality and reduce thermal stress on the body.
Regulating humidity levels is also a factor, as extremely dry air can irritate the respiratory passages already affected by the virus. Aim for a relative humidity level between 40% and 60% for optimal comfort and to limit the viability of the virus. Moderate use of an air conditioner to maintain this range directly supports the person recovering.
How Air Conditioning Affects Viral Spread
The main concern regarding air conditioning and COVID-19 transmission relates to how the system moves air containing respiratory aerosols. When an infected person coughs, speaks, or breathes, they release tiny, virus-laden particles. Air movement created by any system can increase the distance these particles travel within a room or building.
Central HVAC systems recirculate air throughout the entire dwelling. This process can distribute contaminated air from the sick person’s room to other shared spaces. In contrast, a single-room unit, such as a window air conditioner, primarily recirculates air only within the room where it is installed. Central systems require more stringent mitigation strategies to prevent the transfer of infectious aerosols.
The system’s function is primarily to cool the air, not to filter out microscopic viral particles, unless a high-efficiency filter is installed. Air currents from AC units have been implicated in viral spread in poorly ventilated spaces, demonstrating that air movement extends the reach of aerosols. The goal of safer operation is to interrupt recirculation and remove infectious particles.
Strategies for Safer AC Operation
Implementing specific strategies can reduce the risk of transmission while using air conditioning during an infection. The first step involves upgrading the air filter in a central HVAC system to the highest-efficiency filter the unit can handle, ideally a Minimum Efficiency Reporting Value (MERV) 13 or higher. A MERV 13 filter captures at least 50% of the smallest particles, including the aerosolized droplets that carry the virus (typically 0.3 to 1.0 microns).
Running the central system’s fan continuously, rather than only when cooling is active, maximizes the number of times air passes through the high-efficiency filter. Setting the thermostat fan to the “on” position ensures constant air filtration, steadily removing airborne particles. Before upgrading the filter, confirm that the HVAC system can handle the increased resistance to airflow that higher MERV ratings create.
In the infected person’s room, adding a standalone portable air cleaner with a High-Efficiency Particulate Air (HEPA) filter provides extra filtration. These units are effective at capturing airborne particles and should be sized appropriately for the room and run continuously. It is also beneficial to use exhaust fans in bathrooms or kitchens that vent air directly outside, as this actively removes contaminated indoor air.
Introducing fresh outdoor air is important for diluting viral aerosols indoors. Even when the air conditioner is running, slightly opening windows or doors to create a cross-breeze helps replace indoor air with cleaner outdoor air.
If the infected person is isolated, the door should be kept closed. If possible, slightly open a window with an exhaust fan placed in it, blowing air out to create negative pressure. This prevents contaminated air from flowing into the rest of the home. When using any fan, ensure the airflow is not blowing directly from the infected person toward others, which could increase transmission risk.