Ventilation brings in fresh air to the building while removing stale air and odors. Ventilation is important for preventing the build up of common environmental pollutants, such as:
- Dust
- Gases
- Moisture from building processes and activities
- Cleaning products
- Building materials
Ventilation in a building can be from natural sources like windows or mechanical systems.
What type of ventilation is found in homes?
Natural ventilation can come from opening windows and doors. Homes typically rely on natural ventilation for fresh air when they are heated by furnaces and boilers or cooled with window air-conditioning units.
Newer homes and updated older homes may have mechanical ventilation that filters air. Exhaust systems are the most common type of mechanical ventilation in homes. Exhaust systems are often found in bathrooms or kitchens. Exhaust ventilation is important for moving common indoor air pollutants to the outdoors. In buildings that lack mechanical ventilation, the best way to improve indoor air quality is by:
- Opening windows
- Reducing moisture
- Reducing irritant sources
What type of ventilation is found in large buildings?
Larger buildings rely on heating, ventilating, and air-conditioning (HVAC) systems for filtering and distributing fresh air. Larger buildings include:
- Housing with four or more units
- Public schools
- Municipal buildings
- Commercial buildings
HVAC systems in larger buildings include centralized air-handling units or in-room equipment. In-room equipment like unit ventilators supply fresh air and help dilute normally occurring indoor air pollutants. In-room equipment is often found in schools and offices. These types of systems are also designed to return some air from the indoors and vent some air outdoors. Mechanical exhaust ventilation in these types of buildings helps to remove air, odors, and other pollutants.
The design, operation, and maintenance of a ventilation system helps maintain good indoor air quality. It is important to make sure a mechanical ventilation system is operating properly. This requires periodically checking the operation and maintenance of the system.
Indoor air quality and ventilation in public buildings
Air sampling is used to see if a mechanical ventilation system is working properly in high occupancy buildings. This includes measurements for:
- Carbon dioxide
- Temperature
- Relative humidity
The DPH Indoor Air Quality Outreach and Education Unit (IAQ) measures these parameters during a school or public building assessment to check whether the rooms are well ventilated and comfortable.
Carbon dioxide
Carbon dioxide is an odorless, colorless gas that occurs naturally in the environment and in exhaled breath. Elevated levels of carbon dioxide within an occupied room suggest insufficient ventilation. Carbon dioxide levels can show how well a building's ventilation system is working. DPH recommends that carbon dioxide levels be below the guideline level of 800 parts per million (ppm). Above this level, studies indicate increasing reports of:
- Headaches
- Lethargy
- Eye irritation s
- Irritation to the upper respiratory system
DPH IAQ Unit staff can measure carbon dioxide in every occupied accessible room or activity space. These measurements along with an inspection of the ventilation equipment is used to determine if ventilation is adequate.
Temperature and relative humidity
People naturally generate heat and moisture. Complaints of poor air quality are often associated with temperature and humidity. For example, a room may be described as ‘stuffy’, which may suggest that the temperature is too warm. It could also suggest indoor humidity is above a comfortable level. Measuring temperature and relative humidity in all accessible rooms in a building can help determine how well the HVAC system is working.
Temperature changes in occupied spaces are common. DPH recommends that indoor air temperatures be maintained in the range of 70°F to 78°F. Additionally, DPH recommends that relative humidity be maintained between 40 to 60 percent. These ranges are often most comfortable for building occupants.
A sensation of dryness and irritation often occurs when relative humidity is low. This is a very common problem during the winter heating season in the northeastern United States. Low humidity environments contribute to upper respiratory and eye irritation.
In the summer, indoor relative humidity levels are expected to be higher. Relative humidity above 60 percent can contribute to feelings of heat-related discomfort.