Stage Two Petrol Vapour Recovery (PVRII) controls came into force at the beginning of October, meaning sites selling more than 3.5 million litres of petrol a year have until January 1, 2010 to fit equipment to capture fumes at the pump.
Ben Bradshaw, minister for air quality, said the legislation was part of a package of measures to reduce pollution, particularly summer smog.
He said: "The impact of the costs involved has been considered carefully. We want a common-sense balance between the likely benefits for air quality and protecting the viability of businesses. That’s why we are confining the measure to larger service stations.
"Many smaller, rural service stations have a vital role in providing other services to communities and we have set the threshold for fitting the equipment to ensure they are protected."