Savings of energy in buildings is a priority in many countries. The EU Member States took on the obligation to reach highly energy efficient building stock by 2050. Poland, as a member country of the EU, makes efforts to reduce energy consumption in the building sector. The Polish National Centre for Research and Development is an agency of the Minister of Science and Higher Education. It is the entity created as the platform for dialogue between the business and scientific communities. The Board of the National Centre for Research and Development prepares and announces competitions for strategic research and development programmes. A strategic programme

Technical installations of heating, ventilation, and/or air conditioning allow maintaining comfortable and healthy conditions in buildings. Building construction, inter alia, thermal insulation, glazing, etc. and the way buildings are used influence the operation of HVAC systems. The indoor environment and energy consumption of buildings are thus closely interrelated [1,2]. Currently, much effort is paid to decrease energy consumption in buildings. The Energy Performance of Buildings Directive (EPBD) from 2002 and its recast from 2010 assume that new buildings in the near

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A probe of the pressure-balance type has been developed and used as part of an automatic isokinetic dust sampler. The aerodynamic characteristic of the probe was studied in order to determine the gas velocity when using this probe at its location in the duct. Such an anemometric function of the probe, together with an automatic control and logging of sampling parameters, maintains the isokinetic conditions during the sampling of dust-carrying gas and permits the online and in situ continuous measurement of the gas velocity (with uncertainty at the same level as that of typical standard methods). This eliminates the necessity to use separate standard gas velocity sensors that disturb the aerosol movement at the entrance of the aspiration nozzles of dust probes. This in turn ensures a high representativeness of the aerosol aspiration. While being in compliance with the international standards, dust sampling trains equipped with the pressure-balance-type probe with an anemometric function are more accurate from the point of view of the determination of the dust content of flue gases.

Measurements of the amount of dust emitted to the atmosphere together with fl ue gases (after cleaning them) are brought to the determination of the emission mass concentration of dust in the gas s and/or the so-called dust emission rate E (being the fl ux of dust mass) -in the fl ow conduit (duct or stack) at the outlet to the atmosphere. Both of these parameters are the basis for assessment -in various aspects -of noxiousness of the source of dust pollutant emissions.The key concentration of dust s is determined by the measurement. The emission rate is calculated according to the formula E = sV · , where V · denotes the volumetric gas fl ow rate in the conduit. This fl ow rate is calculated according to the relationship V · = w -A, in which A is the area of the conduit cross--section and w -is the average gas velocity in the direction of the duct axis. The latter -by means of a suitable averaging -is determined on the basis of the point profi le of a x i a l velocity w 0 , which is found by measuring. A frequent method and at the same time a reference method of measuring the dust concentration s is the manual gravimetric method based on collecting a dust carrying gas sample at representative points in the duct cross-section and determining the concentration of dust in it. Measurements of distribution of gas axial velocity in the duct accompanying this method are often performed with differential pressure sensors (EN 2001, PN-EN 2007, PN 1994. The classical in use are independent anemometric systems which in the manual version contain Pitot tubes. There are also cases in which gravimetric dust samplers are provided with Pitot tubes mounted on the dust sampling probe near to the aspiration nozzle. In some other -rarer -solutions, gravimetric dust samplers contain a special so-called zero dust sampling probe with the function of a velocity sensor.Known from the rules of fl uid mechanics, the principles of independent measurement of gas point velocity with use of a differential pressure sensor are provided e.g. in the ISO standard (2013) and its counterparts EN ISO (2013) and PN-EN ISO (2013), and also in another ISO standard (1994). They mention the necessity of keeping the practical alignment of a sensor with a direction of gas fl ow. The ideal situation occurs when the gas fl ow at the measuring point inside the Keywords: directional sensitivity, differential pressure sensors of gas velocity, fl ue gas velocity measurements, dust emission measurements, Pitot tubes, zero pressure dust sampling probe.Abstract: Manual measurements of distribution of gas velocity in conduits of fl ue gas installations using systems with differential pressure sensors of velocity are often performed for the requirements of determining emissions of dust pollutants from industrial process plants to the atmosphere. The aim is to determine an axial velocity profi le. Flows in measuring sections are not always coaxial along the run of the duct; they are characterized by different directions of the velocity vector at various measuring poin...