Passive Diffusion Samplers are generating a lot of interest in the environmental community for four main reasons:
•Water samples are more representative of the area adjacent to the well screen or area of interest than those taken by other conventional means.
•Well purging is not required.
•They are simple to deploy.
•They are inexpensive when compared to other sampling techniques.
The principle behind passive diffusion is that compounds will migrate or diffuse through a semi-permeable membrane until a concentration equilibrium is established on either side of the membrane. The following three passive devices are currently commercially available or will be soon.