Environmental technology group, Porvair, said it had made a good start to its 2012 financial year, with pre-tax profits ahead of its expectations.In the four months to the end of March, revenues were 12% ahead of the same period in the prior year. The firm added that during the period order books had strengthened and the outlook for the coming months was encouraging.In its Metals Filtration division sales revenue was 15% higher than the same period in the prior year and margins continued to improve, Porvair said.Its Microfiltration division saw sales revenues rise 10%, while revenue from aerospace grew by 22%.The news cheered investors who pushed the shares up 3% in early trading on Wednesday.