سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 6151)

shows us that indoor air pollution be a much greater danger than outdoor pollution. In one 2009 study, researchers found 586 chemicals in the air of 52 typical homes in Arizona, USA. In today’s society, most people spend up to 90% of their time inside buildings. When there inadequate ventilation and no access to fresh air, all the harmful elements are kept inside. This condition is known “sick building syndrome” and is made worse because we seal our buildings tightly to reduce energy costs How much of their time do most people spend these days?