akna toimeavamine
variable opening up to position to which the sash could be opened during use of the fume cupboard and where a stop device limits further opening unless deliberately overridden, muudetav avanemine asendisse, milleni aknaraami saab tõmbekapi kasutamise ajal avada, ja kus piiraja piirab edasist avanemist, kui seda tahtlikult ei tühistata
