Division: Averaging periods and reference conditions for emissions to air - Commission Implementing Decision (EU) 2017/2117 of 21 November 2017 establishing best available techniques (BAT) conclusions, under Directive 2010/75/EU of the European Parliament and of the Council, for the production of large volume organic chemicals (notified under document C(2017) 7469) (Text with EEA relevance)

Unless stated otherwise, the emission levels associated with the best available techniques (BAT-AELs) for emissions to air given in these BAT conclusions refer to values of concentration, expressed as mass of emitted substance per volume of waste gas under standard conditions (dry gas at a temperature of 273,15 K, and a pressure of 101,3 kPa), and expressed in the unit mg/Nm³.

Unless stated otherwise, the averaging periods associated with the BAT-AELs for emissions to air are defined as follows.

Type of measurement	Averaging period	Definition
For any parameter where, due to sampling or analytical limitations, 30-minute sampling is inappropriate, a suitable sampling period is employed.
For PCDD/F, a sampling period of 6 to 8 hours is used.
Continuous	Daily average	Average over a period of 1 day based on valid hourly or half-hourly averages
Periodic	Average over the sampling period	Average of three consecutive measurements of at least 30 minutes each^f1 ^f2

Where BAT-AELs refer to specific emission loads, expressed as load of emitted substance per unit of production output, the average specific emission loads l_s are calculated using Equation 1:

Equation 1:

l_{s} = \frac{1}{n} \sum_{i = 1}^{n} \frac{c_{i} q_{i}}{p_{i}}

where:

n

number of measurement periods;

c_i

average concentration of the substance during i^th measurement period;

q_i

average flow rate during i^th measurement period;

p_i

production output during i^th measurement period.

Division Averaging periods and reference conditions for emissions to air

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