An air-conditioned and a naturally ventilated museum in a highly polluted part of London were compared for effectiveness of pollution control. Nitrogen dioxide, sulphur dioxide and hydrogen sulphide concentrations were measured inside and outside using diffusion tubes. Airborne particles were measured using a Grimm laser counting device. It was found that the benefits normally attributed to air-conditioning with filtration were not as great as might be thought. Only nitrogen dioxide and particle levels were significantly lower in the air-conditioned museum than in the naturally ventilated museum
