Assessment of occupational exposure to dust

Exposure to dust within the workplace 

Recently, we attended an open plan industrial unit as our client had concerns about the amount of dust their employees were being exposed to during their working day. Situated in a former quarry, the unit has purpose built offices and welfare facilities to the front of the unit, with a large open plan storage area to the rear. The unit is currently used for the storage of scaffolding and other access equipment. During a typical working day, forklift trucks are used frequently and the unit is exposed to the outside environment. 

assessment of occupational exposure to dust

How do we evaluate the amount of dust present?

In order to evaluate the amount of dust present in the workplace, we require samples. We used a 7-hole sampling head fitted with QMA filters (25mm,1.6µm) in order to collect the total inhalable dust samples. Employees were fitted with personal samplers and 7-hole sampling heads fitted with nitrocellulose filters (25mm, 0.8µm) to provide us with samples for the microscopic identification of the dust particles. Small amounts of dust were collected onto the filters which were subsequently cleared by acetone vapour and examined by direct optical microscopy. 

assessment of occupational exposure to dust

Conclusions of air monitoring

The results of air monitoring suggested that the employees are unlikely to be exposed to levels of inhalable dust above the workplace exposure limits (WELs). When comparing the various types of samples obtained in the warehouse and the offices, we noticed that the dust in the offices most likely originates in the warehouse by the abrasion of the existing concrete flooring and dispersion of accumulated outside dust and debris. We examined the dust collected from the office with a microscope, this revealed some typical indoor dust components such as fibres and skin cells and mineral particles with similar properties to those identified in the warehouse. 

Our surveyor believes that the most likely reason for dust transporting from the warehouse to the office area is the transport of suspended dust along the air pressure gradient. Warm air in the offices rises and escapes through the ceiling/roof which creates slightly decreased air pressure in the offices. This lower air pressure then creates a suction-like effect which draws dust contaminated air from the warehouse. Using all the information above, our surveyor was able to conclude that the dust accumulation on the surfaces in the warehouse is not excessive. 

assessment of occupational exposure to dust

Remediation recommendations

On completion of our assessment, our surveyor was able to recommend the most suitable remediation measures based on the conclusions. He recommended that in order to prevent contaminated dust from the warehouse entering the office areas, a fresh air supply should be installed in the offices. The fresh air should be drawn in from the outside area, preferably at the front of the unit and filtrated.

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