Problems with your fume hood's flow rate? It might not be a problem with the air handler.
Be careful with loose Kimwipes, paper towels, tin foil and other such lightweight items when working in a fume hood. These items can get drawn into the fume hood and clog up the ductwork or filters. This reduces airflow, causing the hood to stop functioning properly. These lightweight items are most likely drawn into the duct work when you close the sash, or if they are used close to the baffles at the back of the hood. Keep lightweight items weighted down or secured to another object. Dispose of unneeded papers and foil outside of the hood to keep them from causing problems.