Fenceline Monitoring Tubes

What Is Fenceline Monitoring?

Fenceline monitoring measures airborne concentrations of volatile organic compounds (VOCs) at the perimeter of industrial facilities. It provides a continuous record of emissions at the facility boundary, protecting nearby communities and demonstrating regulatory compliance.

The US EPA issued Methods 325A and 325B under 40 CFR Part 63 specifically for fenceline monitoring of benzene and other VOCs at petroleum refineries. These passive diffusion tube methods use sorbent-packed tubes deployed at multiple fenceline positions for defined sampling periods, then thermally desorbed and analyzed by GC/MS.

EPA Method 325A and 325B

EPA Method 325A describes the sampler deployment and retrieval procedure. Method 325B covers the laboratory analysis using thermal desorption and GC/MS. Together, they define tube specifications, sorbent type (Carbopack X), deployment geometry, blanks, duplicates, and QC requirements.

Camsco manufactures passive diffusion tubes that meet the sorbent, tube material, and dimensional specifications required by Methods 325A and 325B. Our tubes are available preconditioned and sealed for immediate deployment.

Camsco Fenceline Monitoring Tubes

Camsco produces fenceline monitoring tubes in stainless steel, inert-coated stainless steel, and glass. Standard sorbent loadings for Method 325 applications use Carbopack X at specified masses. Custom sorbent configurations are available for non-Method-325 fenceline applications or multi-compound monitoring programs.