Environmental specialists from Germany and Hong Kong said here Friday that more attention should be paid to the indoor air quality, whose potential risk is critical to people's health.

At a seminar entitled "To Improve Outdoor & Indoor Air Quality, " participants stated that the outdoor air quality has been focus for the environmental study, but in fact, the density of pollutants in the air indoors is much higher that outdoors.

Professor Heinrich Holter, president of Holter Technologies Holdings of Germany, said the occurrence of adverse health effects indoors began to increase, as buildings became increasingly sealed with insulation, and windows and brickwork became more airtight.

Holter noted that the reduction of air-change rate leads to a greater concentration of harmful substances, which in non-airtight buildings had previously been reduced by natural air changes.

"For health reasons," he said. "It is known that an air-change rate of 1 to 1.5 is desirable, yet in houses that have been insulated accordingly we only encounter rates of 1.15 to 0.1."

"Therefore, contaminated indoor air is replaced at much too low a rate, leading to an increase in the number of complaints suffered by the occupants of such buildings," he pointed out.

In addition, room humidity levels have increased, leading, above all, to a greater occurrence of moulds and mites as potent allergen carriers, which best thrive at relative humidity levels higher than 60 percent to 70 percent and temperatures greater than 23 degrees Celsius, he added.

Holter pointed out that indoor air pollutants are to a large extent dependent upon the prevailing indoor atmospheric conditions, in particular with regard to ventilation, and, for the most part, upon the air supplied via air-conditioning systems

(From Internet Information Center)