Consider an office whose HVAC system provides 5 air changes per hour to a 40 m3 conference room. Herein, 80% of the supply air is recirculated, and the other 20% is outdoor air ventilation. A filter removes particles from the supply air stream with a 75% efficiency. At 9am, an employee lights a scented candle in this room that emits 6 mg of particles every hour. This conference room hosts a meeting from noon to 1pm. (Assume: = 0.5 h-1 for particles in this room; occupants breathe at a rate of 0.6 m3/h during the meeting. Neglect outdoor particles.)