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The Government of Spain has published a guide with recommendations on the use and maintenance of air conditioning and ventilation systems in buildings and commercial premises aimed at industry professionals. 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 malls, facilities. sports or cultural activities, 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 facilities. 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 occupancy of spaces.
2- It is advisable to verify that the teams in charge of the air renewal work, at least, in their nominal design conditions and that the possible load losses, especially internal to the system are minimal (filters with filling, etc.).
3- If the system has specific air quality controls (CO2 probes, etc.) it is recommended to disconnect, giving priority to the system flow (by schedule). Specifically, during working hours, it is advisable to work with the maximum flow 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 for the system to 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 the recirculation of the air whenever the conditions of operation allow it.
5- Regarding the rotary heat recuperators, it is advisable to carry out an inspection before putting them into operation. In plate recoverers, on the other hand, it is recommended to check for 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 active permanently.
7- When the building, in origin, does not have systems of mechanical ventilation, the guide recommends the opening of accessible windows, favoring the cross ventilation. It is advisable to carry out regular ventilation with windows even in buildings with mechanical ventilation.
8- It is recommended not to change the setpoint or heating or cooling temperature.
9- The regulatory ranges on relative humidity -between 30% and 70% - are considered adequate, so the guide advises maintaining the setpoints previously established in the building.
10- In the event that there are "fancoils", "splits" inductors or other types of indoor units of direct expansion in the building, it is advisable that these devices work in a rhythmic and solidary way with the outdoor units. The guide recommends increasing, as technically as possible, the filtration of recirculated air if the equipment allows it, and as long as the nominal air flow of the equipment is guaranteed.
11- If the premises have difficulties in obtaining satisfactory ventilation, it is advisable to use portable units equipped with high-efficiency HEPA filters, located in the spaces to be treated. They need to maintain a significant hourly movement rate. The effectiveness of these teams depends on their correct selection and sizing, so it must be done by a competent technician. In particular, the guide recalls that equipment based on ozone generation cannot be used in places with people present and that the World Health Organization warns against the use of UV-C lamps to disinfect hands or any another 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 make 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 advisable to carry out a process of purging the indoor air of both the building and the system, for which it would be enough to start the ventilation system to offer a number of adequate indoor air renovations.
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 of rotary recuperators are followed. This recommendation does not exempt from the mandatory review, once per season, of the network of pipes according to the criteria of the UNE 100012 standard.
14- It is advisable to replace the air filters in accordance with the maintenance program already established in each building. If the fan of the equipment allows it, it is recommended to improve the efficiency of the filter, as long as the nominal air flow of the equipment is guaranteed.
15- The document also considers it convenient to review and clean the drive and return units.
16- Maintenance tasks must be carried out in accordance with the safety measures established in the protocols of each company and according to the guidelines of the Ministry of Health. Specifically, the guide emphasizes 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.
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 should begin at least two hours before disinfection work begins. Within the protocol of cleaning and disinfection of the space, it is recommended to include the grilles of impulse and return of air; the extraction, cleaning and disinfection of the filter of the indoor unit if any (fancoil, split); and cleaning and disinfecting the indoor unit, if any, by spraying a disinfectant solution.