It is not yet clear whether air cleaners that can be moved around actually help to reduce transmission of the coronavirus SARS-CoV-2. These findings are from a literature review conducted by RIVM.  

RIVM researched whether portable air cleaners would have an impact if they were placed in ventilated public spaces, such as schools and shops. It is unclear whether these air cleaners lead to reduced human-to-human transmission of COVID-19.

Not enough scientific research

RIVM was unable to find any articles presenting research results specifically focusing on SARS-CoV-2 or other respiratory viruses. Some studies show that portable air cleaners remove bacteria and fungus from the air. However, it is unclear whether fewer people become ill as a result. In 2016, for example, one study showed that absence due to illness was the same in classrooms with or without an air cleaner, although the air cleaner had successfully reduced the number of bacteria in the air. 

Focus on proper maintenance and safety

Proper periodic maintenance is important for air cleaners to be operated safely. If the air cleaners are not well maintained, micro-organisms can grow on filters and be distributed through the room. Some devices can also release harmful substances into the room, such as ozone. More research is needed to determine the potential long-term effects of exposure to these substances.

In the report, RIVM indicates that insufficient scientific evidence is available to support installation of portable air cleaners in public spaces. Further investigation is needed to determine whether air cleaners should be advised. 
In the meantime, they could possibly be placed in some indoor spaces as a temporary precaution during periods when many people have COVID-19. This could be considered in indoor spaces where vulnerable people spend extended periods of time, such as nursing homes. The air cleaners could also be used in indoor spaces with a higher risk of airborne transmission of the virus, such as in busy cafés. In any case, it is important to choose a safe device and ensure proper maintenance.