DAVID SEYMOUR (Leader—ACT): Thank you, Mr Chair. Does the Minister stand by his statement he just made that he's only recently found out the science on high-efficiency particulate air filters versus windows. Does he agree that the time taken to replace the air in a room by opening the window or having a filter inside the room is a function of the flow rate of the filter or window and the volume of air in the classroom? And can he tell us about the new science where that calculation recently became available after he'd ordered the filters?