Division BAT 4 BAT is to monitor emissions to air by using the monitoring techniques with at least the minimum frequency given below and in accordance with EN standards. If EN standards are not available, BAT is to use ISO, national or other international standards that ensure the provision of data of an equivalent scientific quality.

United Kingdom

Description	Unit	Minimum frequency	Monitoring technique
Continuous measurement of SO₂ emissions may be replaced by calculations based on measurements of the sulphur content of the fuel or the feed; where it can be demonstrated that this leads to an equivalent level of accuracy.
Regarding SO_X, only SO₂ is continuously measured, while SO₃ is only periodically measured (e.g. during calibration of the SO₂ monitoring system).
Refers to the total rated thermal input of all combustion units connected to the stack where emissions occur.
Or indirect monitoring of SO_X.
Monitoring frequencies may be adapted if, after a period of one year, the data series clearly demonstrate a sufficient stability.
SO₂ emissions measurements from SRU may be replaced by a continuous material balance or other relevant process parameter monitoring, provided appropriate measurements of SRU efficiency are based on periodic (e.g. once every 2 years) plant performance tests.
Antimony (Sb) is monitored only in catalytic cracking units when Sb injection is used in the process (e.g. for metals passivation).
With the exception of combustion units firing only gaseous fuels.
(i) SO_X, NO_X, and dust emissions	Catalytic cracking	Continuous^f1 ^f2	Direct measurement
	Combustion units ≥ 100 MW^f3 and calcining units	Continuous	Direct measurement^f4
	Combustion units of 50 to 100 MW	Continuous	Direct measurement or indirect monitoring
	Combustion units < 50 MW	Once a year and after significant fuel changes^f5	Direct measurement or indirect monitoring
	Sulphur recovery units (SRU)	Continuous for SO₂ only	Direct measurement or indirect monitoring^f6
(ii) NH₃ emissions	All units equipped with SCR or SNCR	Continuous	Direct measurement
(iii) CO emissions	Catalytic cracking and combustion units ≥ 100 MW	Continuous	Direct measurement
(iii) CO emissions	Other combustion units	Once every 6 months	Direct measurement
(iv) Metals emissions: Nickel (Ni), Antimony (Sb)^f7, Vanadium (V)	Catalytic cracking	Once every 6 months and after significant changes to the unit	Direct measurement or analysis based on metals content in the catalyst fines and in the fuel
	Combustion units^f8
(v) Polychlorinated dibenzodioxins/furans (PCDD/F) emissions	Catalytic reformer	Once a year or once a regeneration, whichever is longer	Direct measurement

Annotations

Footnotes

f1: Continuous measurement of SO₂ emissions may be replaced by calculations based on measurements of the sulphur content of the fuel or the feed; where it can be demonstrated that this leads to an equivalent level of accuracy.
f2: Regarding SO_X, only SO₂ is continuously measured, while SO₃ is only periodically measured (e.g. during calibration of the SO₂ monitoring system).
f3: Refers to the total rated thermal input of all combustion units connected to the stack where emissions occur.
f4: Or indirect monitoring of SO_X.
f5: Monitoring frequencies may be adapted if, after a period of one year, the data series clearly demonstrate a sufficient stability.
f6: SO₂ emissions measurements from SRU may be replaced by a continuous material balance or other relevant process parameter monitoring, provided appropriate measurements of SRU efficiency are based on periodic (e.g. once every 2 years) plant performance tests.
f7: Antimony (Sb) is monitored only in catalytic cracking units when Sb injection is used in the process (e.g. for metals passivation).
f8: With the exception of combustion units firing only gaseous fuels.