Specialist filtration and environmental technology group Porvair said 2014 had begun well and the outlook in the next few months was encouraging.The group, which employs about 600 staff in operations in the UK, US, Germany and China, said revenue in the four months to March 31st had risen 23%.At constant currencies, revenue would have risen 26%, of which 15% was due to several large projects.Porvair, which serves markets including aviation, energy and industrial process, environmental laboratories and molten metals, said underlying revenue growth in constant currencies was 11%."The outlook for the coming months is encouraging. Order books are healthy and the large engineering projects referred to above are progressing according to plan," the group said in a trading update ahead of its first half results on June 23rd.PW