ADR exempts completely private, non-work related carriage subject to some conditions (ADR 1.1.3.1(a)).
Work related carriage may be exempt or partially exempt in three ways:
Ancillary to main activity. ADR 1.1.3.1(c). This is a limited exemption which is discussed in Main Exemptions.[1]
Up to 1 litre of petrol can be carried under the LQ provisions (see Main Exemptions[2]).
- As a "small load"
The small load exemptions (Main Exemptions[3]) will be applicable up to a total quantity of 333 litres (if other dangerous goods are carried the aggregation rules must be applied). The containers must be UN approved (see Packaging[4]) and properly labelled (see Consignment Procedures[5]). Typical 5 litre containers purchased from car accessory shops and garages may not be so approved.
A typical case would be the carriage of two or three jerricans in a van. Providing those cans are UN approved, marked UN 1203 and labelled with the flammable diamond, the only requirements are
- Driver training in accordance with ADR 1.3
- Carry 2 kg fire extinguisher
- Stow the jerry cans correctly to avoid damage or loss from the vehicle
Note: a typical steel jerry can might be marked 
3A1/Y/170/**/GB/****
** is the year of manufacture and **** the packaging certificate number.
In this case no density figure is give after the "Y" which means it is suitable only for liquids with relative density ≤ 1.2 (petrol is typically 0.8 or less)