The Air Quality Limit Values (Scotland) Regulations 2001 No. 224

SCHEDULE 1 LIMIT VALUES, MARGINS OF TOLERANCE ETC.

PART II NITROGEN DIOXIDE (NO₂) AND OXIDES OF NITROGEN (NO_x)

Alert threshold for nitrogen dioxide

2.2  400 μg/m³ measured over three consecutive hours at locations representative of air quality over at least 100 km² or an entire zone or agglomeration, whichever is the smaller.