It is recommended that air exiting a fume hood should be passed through a HEPA filter and exhausted outside the work environment, with used filters being handled as hazardous waste. Turbulence can cause nanomaterials to exit the front of the hood, and can be avoided by keeping the sash in the proper position, keeping the interior of the hood uncluttered with equipment, and not making fast movements while working. High face velocities can result in loss of powdered nanomaterials; while as of 2012 there was little research on the effectiveness for low-flow fume hoods, there was evidence that air curtain hoods were effective at containing nanoparticles.[1]:19–24