Thermal testing is usually carried out on bodies that are to be produced serially and the type approval is valid for six years. Batch testing of serially produced bodies is required at a rate of 1/100.
The ATP thermal test is an accurate test where the required conditions are strictly controlled. Where a less accurate test can be accepted for domestic use and refrigeration unit sizing the cost effective but less accurate Cambridge K test can be used (nb This test does not comply to ATP).
See the guide to ATP and the text of the ATP agreement for precise test conditions.