Window ventilation, secondary air units and co – Proper ventilation at home and in the office

Whether at home or at work, when it gets cold outside, the windows are opened less often for reasons of comfort. Adequate ventilation is important in all seasons – perhaps even most important in winter, when infections spread faster.

Viruses and bacteria can be spread by droplets and aerosols. As the droplets sink to the ground, the aerosols continue to float in the air. The only way to dilute them and reduce the risk of infection is to change the air.

We present three possibilities for air exchange and explain what needs to be considered in each case.

CO2 measuring devices help with window ventilation

The most obvious, free and above all uncomplicated way is window ventilation. But for it to be effective, it must be carried out correctly and at regular intervals.

Ideally, work rooms should be ventilated before work begins, but at the latest when the employees start work.

As a rule of thumb, offices should be ventilated at least every 60 minutes, conference rooms where people often spend time in confined spaces should be ventilated at least every 20 minutes. In times of an increased risk of infection, the window should be opened more frequently if possible.

When airing the room, the window should remain open for 3-10 minutes, depending on the size of the room, air pressure and wind force. Continuous ventilation through a tilted window can also help to prevent infection. In any case, however, the following applies: The well-being of people in the room must not be impaired by too high or too low a temperature or drafts.

CO2 measuring devices can provide a good indication of when it is time to ventilate. The concentration of CO2 should not exceed 1000ppm. Measuring devices with different functionalities are available for private and professional use.

UNI-T’s A37 CO2 meter, for example, is well suited for living rooms and displays not only the CO2 value but also room temperature and humidity. If the threshold value is reached, an acoustic-optical signal is emitted. Before this, emoticons show how the air quality in the room is. Calibration can be carried out either automatically or manually.

The CO2 traffic light GS 42.01 pro from müller was developed for use in schools, offices, fitness studios, restaurants or other premises where several people are present. The CO2 value can be read quickly and easily via the colour of the LED. Indicator tones can also be activated. The device can be operated intuitively and its minimalist design is unobtrusive.

It is also possible to build a CO2 meter yourself with a little manual skill.

Ventilation and air-conditioning systems: Use filters and ultraviolet radiation

Ventilation systems are characterised by the fact that they transport air into indoor spaces and change it in the process, for example cooling/heating, cleaning or humidifying/dehumidifying. While some systems convey a high proportion of fresh outside air into the room, others treat mostly “used” room air again. This is done by cleaning the air and adjusting the temperature and is much more economical than a pure outdoor air system. On the other hand, these options are less effective when it comes to infection control.

For a system to be infection-proof, it must be set up, operated and maintained properly AND operated exclusively with or to a high degree with fresh air OR have suitable filters or similar. In order to reduce the risk of infection, the proportion of outside air in the system can be increased and that of recirculated air reduced. It is also best to operate the system at least two hours before and after working hours, ideally it should even be in continuous operation.

Since recirculated air has a significantly higher risk of infection, additional methods of air treatment must be used. For example, filters can be installed or short-wave ultraviolet radiation (UV-C) can be used. Class H13 or H14 particulate matter filters, so-called High Efficiency Particulate Air Filters (HEPA filters), with appropriate pre-filtration should be used on filters. Fine dust filters of the group ISO ePM1 > 70 % (previously F8) or ISO ePM1 > 80 % (previously F9) are also suitable. Radiation and filters can be combined for even better protection. How effective radiation is has not yet been fully researched. In any case, however, workers must be protected against radiation.

Secondary air units as a valuable contribution to infection protection

Devices such as fans, mobile air conditioners or fan heaters that operate without an outside air supply are called secondary air units. How effective they are in preventing infection depends on the type of device. Some are able to dilute the room air in a small area and thus contribute positively to protection. However, if an air flow is directed from a sick person to a healthy one, the risk of infection increases considerably.

Therefore, a separate risk assessment must be carried out for each device. This must take into account how many people are in a room. Temperature and noise factors must also be considered. In addition, nobody in the room must be exposed to draughts through the secondary air handling unit.

Air purifiers that have a filter system can be an effective additional measure to prevent infection. This is especially true for small rooms such as waiting rooms where many people are present.

Nevertheless, additional fresh air must be supplied through a window or a ventilation system.

The Air Cleaner, for example, is a compact UVC air desinfection unit with a modern design. The radiation effectively kills viruses, bacteria and mould spores. The housing and light traps reliably protect the user from UV radiation. In addition, the unit has particularly quiet motors, making it ideal for workspaces such as doctors’ surgeries, laboratories, restaurants, conference rooms or even nursing homes.

For home use, the Mi Air Purifier 3H is the ideal companion. As it also cleans rooms of allergens such as house dust, pollen, cigarette smoke or fine dust, it is particularly suitable for allergy sufferers. It has a 3-fold filter system and can be easily controlled via touch screen on the device, via app or voice control.

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