The Government publishes recommendations on the use of air conditioning and ventilation systems to prevent the expansion of COVID-19

The document establishes a series of technical criteria to protect public health, with the aim of preventing the spread of COVID-19 in public spaces and premises with mechanical ventilation or air conditioning, such as offices, shopping centers, sports or cultural facilities, among others.

The guide has been coordinated by technicians from the Ministry of Health, the Ministry of Ecological Transition and Demographic Challenge and the Institute for Diversification and Energy Saving, with the participation of experts in public health, environmental health, aerobiology and air conditioning and ventilation. The recommendations of international agencies, professional organizations and scientific societies have been taken into account.

The recommendations are as follows:

1- The guide emphasizes that air renewal is the most important parameter. If possible, a minimum of 12.5 liters per second (l / s) and occupant is recommended, which is the value that the Regulation of Thermal Installations in Buildings attributes to good quality air. To ensure this minimum value, you can work in two directions: increase ventilation or reduce the occupation of spaces.

2- It is advisable to verify that the equipment in charge of air renewal works, at least, in their nominal design conditions and that the possible pressure losses, especially internal to the system, are minimal (filters with clogging, etc.).

3- If the system has specific air quality controls (CO2 probes, etc.), it is recommended to disconnect them, giving priority to the flow of the system (per hour). Specifically, during working hours, it is advisable to work with the maximum flow rate allowed by the system from two hours before opening and up to two hours after closing. In the remaining hours of the week, including weekends, it is preferable that the system continue to operate at low flow, but never below 25% of the nominal air flow.

4- In those devices that make it possible, the guide recommends eliminating or reducing air recirculation whenever operating conditions allow it.

5- As for the rotary heat recovery units, it is advisable to carry out an inspection before putting them into operation. On the other hand, in plate recuperators, it is recommended to verify possible leaks.

6- If there is a specific extraction system for the toilet area or other areas attached to the office -such as, for example, changing rooms-, it is advisable to keep them permanently active.

7- When the building does not originally have mechanical ventilation systems, the guide recommends opening accessible windows, favoring cross ventilation. Regular window ventilation is recommended even in buildings with mechanical ventilation.

8- It is recommended not to change the setpoint temperature for heating or cooling.

9- The regulatory ranges on relative humidity – between 30% and 70% – are considered adequate, so the guide advises to keep the previously established set points in the building.

10- In the event that there are "fan coils", inductor "splits" or other types of direct expansion indoor units in the building, it is advisable that these devices work in a coordinated manner and in solidarity with the outdoor units. The guide recommends increasing, as much as technically possible, the recirculated air filtration if the equipment allows it, and as long as the equipment's nominal air flow is guaranteed.

11- If the premises have difficulties in obtaining satisfactory ventilation, the use of portable units equipped with high-efficiency HEPA filters, located in the spaces to be treated, is recommended. They must maintain a significant hourly movement rate. The effectiveness of these equipment depends on their correct selection and sizing, so it must be done by a competent technician.

In particular, the guide reminds that equipment based on ozone generation cannot be used in places where people are present and that the World Health Organization warns against the use of UV-C lamps to disinfect hands or any other surface of the skin. Therefore, its use is not recommended in environments where people are present.

12- The document considers maintenance tasks as relevant as those of system operation. Thus, in the case of those buildings and establishments that have closed or ceased their activity, it is advisable to carry out a general review of the air conditioning installation before reopening, cleaning grilles, diffusers, filters and batteries. And if the installation is for ventilation, it is convenient to carry out a process of purging the interior air of both the building and the system, for which it would be enough to start the ventilation system to offer an adequate number of renovations of the interior air.

13- The guide does not consider it mandatory to clean the ducts if the previous recommendations on increasing the supply of outside air, absence of recirculation and stopping rotary recuperators are followed. This recommendation does not exempt the mandatory review, once a season, of the duct network according to the criteria of the UNE 100012 standard.

14- It is advisable to replace the air filters according to the maintenance program already established in each building. If the equipment fan allows it, it is recommended to improve the efficiency of the filter, as long as the equipment's nominal air flow is guaranteed.

15- The document also considers it convenient to review and clean the drive and return units.

16- Maintenance work must be carried out in accordance with the security measures established in the protocols of each company and according to the guidelines of the Ministry of Health. Specifically, the guide stresses the need to act safely in the event of filter changes. Protective measures will be the usual ones, including mandatory respiratory protection and gloves for all of them.

17- In the event of a possible positive case of COVID-19, it is recommended that the space where the person has stayed be ventilated for at least four hours. Ventilation must begin at least two hours before starting disinfection work. Within the space cleaning and disinfection protocol, it is recommended to include the air outlet and return grilles; the extraction, cleaning and disinfection of the filter of the indoor unit, if any (fan coil, split); and cleaning and disinfection of the indoor unit, if any, by spraying a disinfecting solution.

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