Larger vans, minibuses & specialist diesel vehicles
From 3 January 2012, larger vans, minibuses and other specialist diesel vehicles will be affected by the Low Emission Zone (LEZ) for the first time. If you own this type of vehicle, it must meet certain emissions standards to be driven within the LEZ without paying a daily charge.
It doesn't matter whether your vehicle is used for commercial or private purposes - it will still need to meet the standards.
Vehicles affected from 3 January 2012
The age and weight of a vehicle indicate the level of emissions it produces.
http://www.tfl.gov.uk/roadusers/lez/17700.aspx