Industrial Ventilation System Analyses

Ventilation system assessments are typically performed to address indoor air quality concerns, exposure control issues, and operational airflow versus design specifications. Air velocity measurements are made using a velometer/anemometer which provides readings in feet per minute (ft/min) and can be collected at a variety of locations including the face of a laboratory fume hood, air supply and return duct registers in an office environment or manufacturing facility, or at the duct opening of a local exhaust ventilation system.

Laboratory fume hood velocity measurements are recorded using a grid pattern across the face of the hood to effectively calculate an average hood-face velocity. Measurements can be taken during various fume hood setups with the sash positioned at different heights and/or the exhaust fan operating at various settings. The average velocity measurements are then compared to the range of 60 to 100 ft/min recommended by OSHA in 29 CFR, Part 1910.1450 Appendix A and the range of 80 to 100 ft/min recommended by ACGIH. The goal of such measurements is to find the appropriate sash height and fan setting to create a uniformity of hood-face velocity grid measurements and minimum static or turbulent readings in any one area of the grid. No face velocity measurement should have more than plus or minus 20 percent of the average as recommended by the American National Standards Institute (ANSI) and the American Industrial Hygiene Association (AIHA).

Face velocity measurements are also collected for local exhaust ventilation (LEV) systems. Analysis of a LEV not only consists of air velocity measurements, but also includes proper positioning with regard to the workpiece and visual observations of the contaminant plume in determining adequate capture velocity. As with most industrial ventilation system analyses, personal air monitoring can be conducted in conjunction with the LEV adjustments to determine adequacy of the LEV system with regard to employee exposure. HygieneTech has performed airflow studies in various industrial settings, such as paint spray booths and firing ranges, to determine the air flow capabilities of the ventilation systems and if design specifications have been met with regard to employee exposure. These type of analyses also involve personal air monitoring as well as an assessment of standard operating procedures with focus on employee positioning with regard to being upwind of the contaminant plume.

A typical indoor air quality survey for an office environment will include an assessment of the ventilation system to ensure an adequate supply of fresh air is being supplied to the office environment. Adequate fresh air supply can be determined in one of two ways: air velocity measurements can be collected at supply air registers and adequate airflow can be determined based on the size of the subject room, air changes per hour, and the employee occupancy; and/or, carbon dioxide (CO 2) readings can be collected in the indoor environment of concern and this data can be directly compared to guidelines established by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) for building occupant comfort. Based on historic studies performed by HygieneTech, building occupant complaints of “stuffy” air often begin when CO 2 levels exceed 800 parts per million (ppm). HygieneTech has also found that some sensitive persons may experience discomfort, including eye irritation and headache, when CO 2 levels reach 1,000 ppm. Such symptoms are not believed to be the result of an unhealthful exposure to CO 2 ; rather, they are thought to be the result of exposure to other common indoor air pollutants which, if not exhausted and/or diluted, can accumulate over time.