Intertek shares jumped by 6%, or 99p to £16.76 by 9:05am after the product testing company lifted its full-year revenue forecasts.
The company said in a statement: "Environmental regulations, the expansion of renewable energy industries and consumers' concern over the health and safety of their products continue to drive good growth and offset some weaker markets."
Intertek said first-half revenue rose 4.9% to £652m, while pre-tax profit gained 3.3% to £97m.
Its shares posted the largest increase in the FTSE 100 Index, which traded 86 points higher, or 1.6%, to 5,344 points.
