Indoor Environmental Specialists
Welcome to Environmental Diagnostics Corporation (EDC). Managing indoor environments is easier with the proper documentation from experienced professionals. Our highly commended proactive, reactive, and mold assessments, cutting edge sampling methods, and interpretative tools make EDC a leader in the industry.

Ventilation Carbon dioxide measurements in a commercial building are typically the most economical way to determine ventilation performance. Two methods of recording carbon dioxide levels are possible:

  1. spot measurements in numerous locations and/or
  2. long-term (days to months) trend analysis in one or more selected locations.
In any case, understanding the ventilation status of a building is an important component in the comprehension of the quality of the indoor environment. A complete indoor air quality assessment, whether pro-active or as a result of an air quality complaint, should always consider the ventilation status.

ASHRAE recommends the levels of carbon dioxide for the indoor environment not exceed 700 ppm above the outdoor level. Measurements taken in a building during a typical working day should have occupant density levels that are not significantly above or below the norm.

Ventilation and Design
In determining the specific applicable ventilation rate for the HVAC system of a building, some research into the design history of the building as well as building codes in force at the time the building was designed is required. Currently all building heating, ventilation, and air-conditioning (HVAC) systems being designed and constructed must meet the local mechanical codes adopted by local jurisdictions. This means that if you built a building in a particular city today, you must adhere to that city's current mechanical code requirements.

Every state and some of the major cities have building codes, inclusive of design ventilation rates, from which design engineers must use to design a building. The building codes are adopted from organizations such as, the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). ASHRAE is an engineering organization that pools the talents and knowledge of their industry to publish guidance documents on the design principles including the design specifications for HVAC ventilation. These guidance documents are reviewed and subsequently approved by ASHRAE and other industry organizations. Following this, state and local building code agencies may adopt these guidelines making them the requirement for designing a building. Furthermore, most current building codes pertaining to ventilation are standards only for the way buildings in a particular jurisdiction must be designed; they are not enforceable standards for the way the buildings are operated. A few states, through recently promulgated regulations, pending legislation, labor agreements and other mechanisms, are working to apply existing design codes and standards to building operations.

After achieving industry consensus in 1989, ASHRAE published it's "Standard 62-1989: Ventilation for Acceptable Indoor Air Quality." This is a voluntary standard for "minimum ventilation rates and indoor air quality that will be acceptable to human occupants and are intended to avoid adverse health effects". This standard applies to all types of facilities, including dry cleaners, laundries, hotels, dormitories, retail stores, sports, amusement facilities, and teaching, convalescent and correctional facilities. The specified rates at which outdoor air must be supplied to each room within the facility range from 15 to 60 cfm/person, depending on the activities that normally occur in that room. Currently, HVAC systems designed for buildings built in the Washington, DC area likely use ventilation rates set out by ASHRAE 62-1989. Also of note Standard 62, which has been converted to a continuous maintenance document, is receiving considerable attention as it evolves.

To determine the designed ventilation for a particular building, the following information is required.
  • The year the building was designed
  • The ventilation code in force at the time of design
  • If the HVAC system had been replaced and when
  • Number of people for which a building or specific area in a building was originally designed
  • The purpose the area was designed for (i.e. conference room, reception, office space)

Items that can affect outside air volume and proper distribution to occupied areas:
  • Outside air intake volume damper position
  • Active (fan powered) or passive outside air intakes
  • Cycling of air handling units
  • Variable air volume box damper position
  • Balancing damper position
  • Tenant obstructions of supply and return grilles.
  • Window based units with outside air intakes

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