This product is a chitosan film biosensor for heavy metals detection. Chitosan is a biopolymer which produced from the waste product of crustacean shells such as shrimps, crabs, lobsters, etc. The biosensors are fabricated by depositing chitosan solution on a substrate under the influence of certain DC voltage. The electrical testing of sensor¿s properties was carried out in a lab scale to obtain the reliable biosensors. The different heavy metals concentration were measured by exposing heavy metals molecules carried away through the air flow onto the surface of chitosan biosensor. This is a novel technique for detecting heavy metals concentration in a liquid because without a dipping process even though the working mechanism of the biosensors is based the direct interaction between sensitive layer and measurend. Most of techniques to determine the amount of heavy metals in a liquid are based on a dipping process for a direct interaction which often causes the swelling problem and contamination, or using an optical signal for an indirect interaction which usually shows low selectivity.