The bacterial filters from Legend Medical come in two forms: bacterial viral filter (BVF)and heat and moisture exchanger filter (HMEF). The bacterial filter features minimum dead space for better filtration efficiency and low flow resistance. The HMEF has the combined functions of bacterial/viral filtration and heat moisture exchange. The minimized dead space and weight is designed for easy breathing. While electrostatic hydrophobic membrane protects against cross-contamination, the hygroscopic membrane retains exhaled moisture for heat exchange and humidification.