The Heating and Air Conditioning System must also be considered in creating a healthy bedroom.  Up to forty pounds of dust accumulates in an average size house every year.  A mixture of organisms and dirt; dust can aggravate allergies or even carry disease.  Installing traditional and electronic filters in HVAC systems is one way to reduce the problem.  A better way of addressing the problem in the bedroom specifically is through the use of air purifiers and dehumidifiers.  In addition, if a fireplace is present in the bedroom, it should be checked for proper ventilation.  Improperly vented fireplaces in an enclosed space can lead to dangerous carbon monoxide levels.