In most older office spaces these days, there is no provision for ventilation, ie. exhaust of stale air and introduction of fresh, filtered air. Too many consider that just opening a window is all that's necessary, but if you are in a busy town, with traffic levels that they are today, outdoor air can't really be considered as 'fresh'.
Natural ventilation only occurs when the wind is blowing against the building, causing pressure changes.
The only way to provide the quality of air we should really have is through a proper ventilation system. This gets rid of stale odours, alleviates 'sick building syndrome' and the reason for staff sicknesses and absenteeism.
ACCORD AIR SYSTEMS recommends the use of heat recovery ventilator units. These incorporate input and extract fans, heat exchanger, and pre-filter. The purpose of this is to provide a balanced amount of exhausted stale air and introduce fresh air without losing all the heat/cool energy from the exhausted air. These units are designed to recover energy from the outgoing air and transfer that energy to pre-treat the incoming fresh air.
Some manufacturers of heat recovery ventilator units -
Daikin, Mitsubishi Electric, Hitachi, Toshiba, Vent Axia, Baxi, Xpelair, Villavent, LG, Helios, Johnson & Starley, ABB-Flakt