Evaluation of international ventilation and air cleaning guidance generated during the covid pandemic

The project aimed to make an inventory of hands-on ventilation and air cleaning advice that was shared with the general public and e.g. facility managers and building owners during the 2 years of the COVID pandemic. An online search resulted in 188 documents from 16 countries. Many documents addressed the importance of adequate ventilation but did not present concrete advice on how or how much to ventilate to make spaces 'covid safe enough'. Several documents mention the options of CO2 monitoring but only as a rudimentary mean to estimate airborne infection risks. A substantial amount of documents explained that also air cleaning technology can help to decrease infection risks. But not as a substitute for regular fresh air supply, more as an addition to it. Some documents mentioned the effect of (increased) temperature and ditto humidity on virus survival rates but most do not give specific recommendations about setpoint changes. On the other hand, several documents do give concrete advice on other HVAC system settings related to e.g. operating hours, recirculation or pressure balances. The outcomes of this study will be used to help construct a new set of Dutch infographics and guidelines that should help non-technical decision makers to better understand how one can use ventilation and air cleaning technologies to decrease airborne infection risks inside.