BS EN 16868 pdf free download

BS EN 16868 pdf free download. Ambient air – Sampling and analysis of airbone pollen grains and fungal spores for networks related to allergy – Volumetric Hirst method.
4 Principle Ambient air is sampled by a volumetric suction system and directed towards a suitably coated sampling surface through a specific orifice oriented towards the wind; the particles contained in the sampled air are deposited by impaction on a continuously moving adhesive acceptor surface. The deposit on the sampling surface is examined with an optical microscope in order to identify and count the pollen and fungal spores per area (deposition rates). Using this method allows to calculate concentrations as a daily mean or an hourly mean. The sampling is usually done at low-volume rate (10 l/min). It allows a continuous sampling for up to seven days [7] [8] [9]. 5 Sampling 5.1 Equipment 5.1.1 Apparatus The sampling device and its functional principles are shown schematically in Figures 1, 2 and 3. The complete sampling system (so called “trap”) containing the motor, the vacuum pump, the orifice, the rotating drum, the wind vane, the clockwork system, the impaction support shall be: 一resistant to corrosion; -well attached (ie. resistant to wind-blow, etc.); -always horizontal (at the head level). The commercial devices that meet the requirements are presented in Annex A. For the different purposes, refer to the specific publications. The wind vane allows permanent rotation of the trap head so that the orifice faces the wind. The rain shield ensures a weather protection for the orifice [i.e. rainfall).5.1.1.1 Suction pump The suction pump works 24 h a day and continuously throughout the year at the same flow rate. The power supply may be either mains or battery driven (solar panels). The electric motor is capable of continuous operation. The suction system is, for instance, a vacuum pump. The flow rate of suction shall be regularly controlled and adjusted accordingly. The recommended flow rate is 10 l/min with a maximum permissible deviation of+ 10 % (+1 l/min). The manufacturer shall ensure the flow specification and provide a flow verification and calibration procedure that allows the user to ensure compliance with this specification throughout the life of the trap. The validity of the calibration method recommended with an error of less than 10 % in the accuracy of flow rate between calibration and operation shall be certified by the manufacturer. As the accuracy of the calibration depends on the air resistance and characteristic curves of the individual trap, vacuum pump and flow meter used [10], the validity has to be certified accordingly, i.e. specifically for the trap/vacuum pump/flow meter combination delivered by the manufacturer. The flow rate shall be checked at every change of the impaction support.5.1.1.2 Orifice (inlet) (Figure 2) The orifice shall have the following dimensions (with associated tolerances): 一 rectangular opening: 14 mm (+0,1 mm) x 2 mm (+0,1 mm); 一specific orifice length: from 19 mm to 25 mm; 一distance D from the inside orifice to the drum without the tape: 0,70 mm (+0,1 mm). The depth allows the non-turbulence of laminar flow and directs the mixture of air and particles towards the coated support. In consequence, an efficient particle impaction for pollen grains and fungal spores, induced by the laminar flow, is ensured. The distance D between orifice and drum shall be 0,70 mm (+0,1 mm) (see Figure 4 – distance D= A-B). The distance D allows efficient particle impaction for pollen grains and fungal spores. It shall be controlled [11] [12] [13]. The orifice should be directed into the air-stream using a wind vane.BS EN 16868 pdf download.