Heavy Metal Analysis

The MINIVOL Sampler

The MINIVOL portable samplers used were made by Airmetrics (Springfield, OR, USA). This active sampler is operated by the principle of inertial impaction using a single stage impactor with an after-filter. In this device, a pump is used to maintain a constant air flow at a design rate through the impactor and filter, the particle-laden air is accelerated through one nozzle and the exiting jet impinges upon a plate. The large particles cross the air streamlines and impact on the plate due to their inertia, while the small particles are carried along the air streamline and are collected on the after-filter. The mass collected on the pre-weighed filter is then determined by the gravimetric method in the laboratory. The inlet impactor is capable of removing particles larger than the cut points of either 10 �m or 2.5 �m in aerodynamic diameter (50% effective). The method used in this sampling device is a modification of the standard PM₁₀ reference method outlined in the Code of Federal Regulations. The sampler meets the specifications in the Code on the air-inlet system, flow control device, flow rate measurement means and timing control device. However, it is operated at a constant volumetric flow rate of 5�L/min at ambient conditions, which is generally less than the flow rates used by a reference method device. Due to its low flow rate of 5 L/min and the low noise from its pump, MINIVOL samplers with both the PM₁₀ and PM_2.5 inlet impactors were used in the pilot study to measure the indoor (inside the residence) PM₁₀ and PM_2.5 concentrations, respectively.