Overspray

Overspray refers to the portion of a sprayed material that does not reach the intended target and instead deposits on unintended surfaces, remains suspended in the air, or is otherwise wasted. It is a common phenomenon in spray coatings, painting, industrial finishing, agricultural spraying, and aerosol applications.

Causes include high spray pressure, inappropriate nozzle type or size, excessive distance, operator speed, wind, poor ventilation, substrate geometry, or improper spraying technique. In enclosed spaces, airflow patterns can carry droplets away from the target.

Consequences include material waste, environmental contamination, property staining, and health risks to workers from inhalation of solvents, particulates, and vapors. Overspray can also affect adjacent surfaces, equipment, and ecosystems, leading to regulatory and cleanup costs.

Mitigation and control: Engineering controls such as spray booths, downdraft or cross-draft ventilation with appropriate filtration, enclosures, and containment; use of masking, curtains, and containment barriers; proper nozzle selection and lowering spray pressure; electrostatic or air-assisted technologies to improve transfer efficiency; drift-reducing nozzles and nozzle tips in agriculture; process optimization and maintenance. Administrative controls include training, job planning, and scheduling to minimize exposure.

Measurement and management: Transfer efficiency or yield is used to assess overspray; collectors, wand tests, and film-thickness measurements help quantify drift. Standards vary by industry, and regulatory agencies may set drift and emission limits for paints, pesticides, and solvents.