We have attended a dental a laboratory where the employees were being exposed to a relatively loud noise from various types of machinery. As usually performed during workplace noise exposure assessment we have talked to the laboratory manager who talked us through the daily routine and tasks perform in the laboratory by various people. Once we became familiar with the set up and who was doing what we have prepared an assessment plan and started taking some measurements.
First and foremost, we have collected some nose measurements from the ambient noise in the laboratory. The ambient noise is an important factor in workplace noise tests because it can be one of the major contributor in the overall noise exposure. This is particularly the case is high noise environments where activities happening on one side of the production floor are affecting people working in other places.
Once this task was completed we have progressed to assess the noise contribution of every task and tool used in the laboratory. Not all the tools necessarily require testing and evaluation but all the tools should at least be tried to gauge the noise output and likely contribution to the overall exposure. Very quiet tools such as some micro drills, mills or even large drill are so quite that they do not effectively play any significant role on employees’ noise exposure.
We have measure noise output of some of the drill which were emitting noise in the range of 65-75 db(A), extraction tools 75-80 db(A) and some ventilated heating plates which were surprisingly emitting noise at close to 85 dB(A). Once we have measure noise from the main tools and machinery we have looked for other pieces of equipment that could be potentially be contribution to noise exposure. At this stage the tools that are only used rarely or for very short periods of time must be identified and accounted for in the overall exposure assessment. For example, employees often use compressed air nozzles to clean themselves or work pieces form excessive dust. These devices are often used for couple seconds at the time but the exposure can quickly add up if the use is frequent. Based on our experience the compressed air nozzles are typically used for up to 15 minutes a day by employees for cleaning.
Once the noise measurements were completed we have calculated the typical likely workplace exposure levels of the employees working in the laboratory. Some of the employees working in certain parts of the laboratory were being exposed to noise well below the lover action limit of 80db(A). In their cases the major noise contributors were typically radios.
The other group of employees working behind the laboratory desks were being exposed to noise just above 80dB (A). This does not appear as much but when compared to the typical ambient noise in the laboratory of about 60-65 dB(A) this represents a major increase. We have identified thee local exhaust ventilation system to be the culprit. The desks were equipped with desk mounted extraction systems to control dust exposure from some activities.
As the extraction systems is an important part of the overall risk control in the laboratory it cannot be disabled just because it makes noise. The systems was a newly install system and therefore replacement was an acceptable solution to the customer. Fortunately, the extraction motor of the was designed in such way as to allow easy access and variable mounting. This allowed us to remove the motors from the desks. We have extended the pipework of the system and re-positioned the motors to an unoccupied area thus completely removing the offending noise source from the working environment.