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Health concerns arising from low frequency sound in a chemistry lab.

Health concerns arising from low frequency sound in a chemistry lab. Bill Gibson, Environmental Health and Safety Officer, Risk Management Office, Trent University. Initial Report of Illness. September, 2006, Voice mail: Staff member working at a computer in a research lab had “passed out”.

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Health concerns arising from low frequency sound in a chemistry lab.

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  1. Health concerns arising from low frequency sound in a chemistry lab. Bill Gibson, Environmental Health and Safety Officer, Risk Management Office, Trent University

  2. Initial Report of Illness September, 2006, Voice mail: Staff member working at a computer in a research lab had “passed out”.

  3. Investigation • Several staff (not all) experiencing periodic bouts of illness; • Illness appeared to be limited to a single research lab; • Rapid recovery on leaving the lab (less than one hour); • Symptoms had been experienced for about one week.

  4. Investigation Reported symptoms include: • Nausea • Dizziness • Inability to focus • ‘Faint’ feeling (no actually loss of consciousness) • Some reported feeling a ‘pressure change’ in the lab

  5. Investigation • Lab work temporarily halted • Consultations included • Lab staff including Principal Investigator (review of lab operations) • Science Facilities Manager • Physical Resources (Mechanical/Electrical) staff and a review of air supply/exhaust systems (physical and reports) • Third party Environmental Consultants, colleagues

  6. Investigation • Lab involved with studies of biogeochemistry of freshwater • Carbon dioxide <<1000 ppm • No evidence of combustion gases • No evident source of contamination

  7. Investigation • Lab staff agreed to resume work and keep diary of symptoms, but symptoms return by mid-morning; • PI researched symptoms of exposure to sound <20 Hz and found a good match with symptoms; • Pinchin Environmental retained to conduct a sound survey

  8. Chemical Sciences Building • Opened September, 2004; • 35,532 sq. ft. • Houses • Chemistry Department • Teaching labs • Research labs (Chemistry, Environmental Science) • “State-of-the-Art”

  9. Chemical Sciences Building

  10. The Survey • Acoustic data measured with a Bruel & Kjaer (B&K) Model 2260 Precision Integrating Sound Level Meter configured in 1/3 octave mode.

  11. The Survey

  12. The Survey

  13. The Survey • Sound level distribution is consistent with an acoustic mode: Droom =N(wavelength of sound/2); N an integer 1,2,3,…

  14. The Survey

  15. Conclusions • Sound peaks occur in this lab, where room dimensions ‘match’ the wavelength of the sound • Low frequency sound explains the illness experienced when working at the fume hoods at either end of the lab.

  16. Conclusions • The main fumehood duct appears to be generating the low frequency sound; • Attempts to confirm these findings by changing the exhaust fan RPM failed then the entire system shut down (believed due to control system issues)

  17. The Solution • Inhibit motion of the duct walls by installing neoprene-lined ‘hoops’ at several locations on the duct.

  18. Follow up • Separate maintenance concerns led to the discovery that one of the fume hood dampers had worked itself closed; • Re-opening the damper reduced static pressure, duct vibration and fan RPM; • There have been no further reports of health concerns; • Hoops have not been installed.

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