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Building Envelope
Published in Moncef Krarti, Energy Audit of Building Systems, 2020
Tracer gas techniques are commonly used to measure the ventilation rates in buildings. By monitoring the injection and the concentration of a tracer gas (a gas that is inert, safe, and mixes well with air), the exchange of air through the building can be estimated. For instance, in the decay method, the injection of a tracer gas is performed for a short time and then stopped. The concentration of the decaying tracer gas is then monitored over time. The ventilation is measured by the air change rate within the building and is determined from the time variation of the tracer gas concentration: ct=co·e−ACH·t
Indoor Air Quality and Ventilation Measurement
Published in Dejan Mumovic, Mat Santamouris, A Handbook of Sustainable Building Design and Engineering, 2018
Lia Chatzidiakou, Benjamin Jones, Dejan Mumovic
The choice of tracer gas is important and should be appropriate for the measurement task. However, all tracer gases should have a several common characteristics. A tracer gas should be safe, inert, unique, measurable, and should not affect the airflow rate in, or the air density of, the test zone. EN ISO 12569 (BSI, 2012) proposes six tracer gases (see Table 3.3.1), of which three have a high global warming potential (GWP) relative to that of CO2. The remaining unique tracer gases are helium and ethylene. The former has a significantly lower density than air and so should be well mixed using fans throughout the test period, although this could adversely affect the measurement of buoyancy-driven natural ventilation. Ethylene is a flammable gas and so it should be handled with great care. Standard 12569 also identifies CO2 as a tracer gas, and although it is not unique in the atmosphere, dissolves in water, and is absorbed by building materials, it is an acceptable tracer gas when a high degree of accuracy is not required. Other tracer gases (not included in Table 3.3.1), such as nitrogen (non-unique), carbon monoxide (toxic to humans), ethane (flammable), methane (flammable), and isobutene (flammable) are indicated by Standard 12569. Their properties should be checked to ensure that they share have the common characteristics of an appropriate tracer gas.
Measurement Techniques
Published in Rodger Edwards, Handbook of Domestic Ventilation, 2006
There are three principle groups of tracer-gas techniques. Constant concentration techniques aim to sustain a target concentration of tracer gas within a space and to monitor its concentration. When tracer-gas concentration falls below the preset target value, injection of more tracer gas is automatically triggered. For a good description of the use of the technique refer to reference1. Simple air change rate determinations can be undertaken (single tracer gas) simply by monitoring the rate of tracer-gas input. Interzonal air movements can similarly be determined by the use of multiple tracer gases, although recirculation of gases becomes an issue. Modern equipment and computing power have made such techniques a viable proposition. Among the equipments available, the Bruel and Kjaer proprietary system is probably the most well known. Constant concentration equipment is extremely expensive and is only within the budgets of well-equipped research organisations and university departments. The major technical difficulty in the use of concentration techniques is stabilising the gas concentrations. In some situations where mixing is not very good, this may be very difficult to achieve. The use of mixing fans during tests may be necessary. There is some uncertainty regarding the effect of this on internal air-flow patterns within the test building, particularly where the building is naturally ventilated. Rapid fluctuations in incident wind velocity, which in turn cause fluctuations in the actual air change rate will make the attainment of steady-state conditions more difficult.
Experimental study of backflow air leakage through an opening from a depressurized enclosure
Published in Journal of Nuclear Science and Technology, 2022
Zeinab Rida, Salima Kaissoun, Corinne Prevost, Thomas Gelain, Eric Climent
Ventilation systems are employed in many applications to maintain a directional airflow at the openings and thus to limit airborne contaminant dispersion. They are necessary with large-scale openings as large doors for different industrial purposes [3], for building entrances equipped with air curtains [4,5], for refrigerated storage spaces and cold rooms [6,7] and for hospital isolation rooms [8]. They have also been studied in food [9,10] and electronic industries [11] and for pharmaceutical applications. Tracer gas is used to calculate the dispersion rate in ventilated systems useful for the assessment of control room habitability [12]. Studies confirm that the directional airflow is disturbed by many unsteady events, such as door opening [13,14], human walking [15] and the presence of temperature gradients [16,17]. In the context of nuclear safety, many studies have been dedicated to quantifying the intensity and the kinetics of the propagation of polluting agents that result from the breakage of static or dynamic confinement in nuclear ventilated enclosures, for example, in the case of fume cupboards or glove boxes [18,19]. Tracing gas technique was used to calculate the dispersion rate in ventilated systems useful for the assessment of control room habitability [12]. Simulation method was established in order to predict the tritium behavior after the tritium leak event should happen in ventilated room [20].
Outdoor and indoor factors influencing particulate matter and carbon dioxide levels in naturally ventilated urban homes
Published in Journal of the Air & Waste Management Association, 2021
Air exchange rate (AER), which is the rate at which ambient fresh air replaces indoor air, was also measured in the living rooms of all sampling sites by the tracer gas decay method. The tracer gas used in this method should be easily detected at low levels and also should not be available in the background air. Therefore, the nontoxic and odorless sulfur hexafluoride (SF6) was used as a tracer gas and dosed up to 10 ppm in the middle of the living rooms and at a height of about 1.6 m. The gas was then left to decay and the rate of decay was used to calculate the AER. The decay rate of the SF6 was measured by the photo-acoustic multi-gas monitor (Innova 1412i; LumaSense Technologies Inc., Santa Clara, CA, USA). The method was applied at the beginning and end of the measurement periods followed by calculation of mean values.
A Novel Method for Determining Infiltration of Mechanically Ventilated Buildings
Published in Science and Technology for the Built Environment, 2020
Ilpo Kulmala, Heikki Parviainen, Ian Hall, Pertti Pasanen
Another widely used way to determine the air flow rate is the tracer gas method, where a gaseous tracer is released inside the building and its concentration is measured (ASTM 2009). The commonly used release methods are decay and constant injection (Persily 2015). In the decay method, the release of the tracer gas is stopped and the decay in concentration is measured as a function of time. The air change rate (infiltration + mechanical ventilation) is then determined from the slope of the logarithmic decay curve. In the constant release method, the tracer gas is injected at a constant rate uniformly into the space being tested and its concentration is measured at known times (ASTM 2009).