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Introduction

This method is generally regarded as a reference compared with other techniques. It is appropriated for the animal housings which are confined at least a little (net windshield or closing on three sides).

The tracing method is based on the release of a known gas quantity. There are basically two manners of defining the tracers gas fluxes in a closed environnement:

• Approch by constant dosing, where the tracers fluxes are measured directly with each time step
• Approach by decrease rate, where a high quantity of tracer is released in volume to measure; when the concentration is homogeneous, the decrease in the concentration will reflect the rate of ventilation at the placed observed.

There are two approaches to deduce the emission starting from the gas concentration measurements:

• One where the concentration of tracer is employed indirectly; initially the houses ventilation flow is calculated, then the ventilation flow is employed to calculate the emission
• The other where the tracers concentrations is employed directly; the gas fluxes are deduced from the ratios of the concentration gradients between the tracer and the other gases.

Equipment

The most important equipments are:

• The equipment for tracer dosing and gas analyzing,
• Amixing equipment that will force the concentration homogeneity without disturbing the animals, which implies to have air speed below 0,2 m.s^-1,
• The climate sensors inside and outside the building,
• Manual sensors to check the homogeneity of the sensors with measurement recording.

In addition, depending on the situation, the sampling tubes might be isolated and heated to avoid condensation inside, the equipment might be protected against heat or dust or even animals if it is located within the animal house.

Guideline details

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