Indoor air quality is commonly viewed nowadays as worse than outdoors due to the use of air conditioning systems (HVAC and A/C units), increased efficiency in building construction, and the use of chemicals (such as cleaners and air fresheners). The US Environmental Protection Agency (EPA) has warned of short-term and long-term health problems such as asthma (and other respiratory complaints), headaches, eye and throat irritation, and fatigue, all of which can be worsened by poor air quality. These issues are more commonly seen in offices and schools due to the lack of introduction of fresh air throughout those buildings.