[EN 15665:2009, 3.4]:way (method) to express the required performance (for air pollution assessment)NOTE Criteria can be, for example, numbers of hours above 70 % RH in living room calculated on a standard week basis, number of minutes to reach 25 % of the initial pollution concentration based on a standard pollutant emission in a toilet, average level of CO2 above outside in bedroom on a 10 hours night with two standard persons.