A valve assembly (50) comprising a three-way connector (51) operatively interconnecting: an inlet (58), an outlet (56) and a vent (66), the inlet (58) being operatively connectable, in use, to an aspirator tube； the outlet (56) being operatively connectable, in use, to a syringe (82)； and the vent (66) comprising a one-way valve (70) permitting, in use, the flow of a fluid out of the three-way connector (51), wherein the inlet (58) comprises a receptacle (60) containing a porous or perforated element (62) which, when dry, permits the flow of gasses into the three-way connector (51), but which when wetted by a liquid, inhibits or prevents the flow of liquid into the three-way connector (51).
