Overview
ISO 22856:2008 - "Equipment for crop protection - Methods for the laboratory measurement of spray drift - Wind tunnels" defines general principles for measuring spray drift potential in controlled wind-tunnel conditions. The standard is intended for comparative assessment or classification of the relative spray drift potential from spray generators (for example, nozzles) or spray liquids. It provides test layout, sampling procedures, environmental controls and calculation guidance for laboratory evaluation of spray drift using wind tunnels.
Key Topics
- Scope and purpose: Laboratory measurement of airborne and sedimenting spray drift to compare spray generators or formulations.
- Wind tunnel requirements: Uniform velocity profile with maximum local variability 5% and degree of turbulence ≤ 8% in the measurement zone; commonly used nominal air speed 2 m·s⁻¹; minimum working section dimensions for field-type sprayers (height ≥ 1 m, width ≥ 2 m).
- Sampling and collectors: Use of passive samplers (commonly PE or PTFE sampling lines, ~1.98–2.00 mm diameter) arranged in vertical and horizontal arrays; minimum 5 samplers for vertical and horizontal profiles; vertical spacing ≤ 0.1 m, horizontal spacing ≤ 1 m and downwind sampling between 2 m and 5 m.
- Test controls: Humidity (reproducible classification at 80 ± 5%), air temperature (commonly 20 ± 1 °C), maximum instrumentation errors specified for air speed (0.1 m·s⁻¹), temperature (1 °C) and relative humidity (5%).
- Measurement outputs: Vertical airborne spray profile and horizontal sedimenting spray profile, quantified typically by tracer recovery using solvent extraction and analytical calibration.
- Operational details: Minimum spray time 5 s, tracer/surfactant guidance (surfactant commonly 0.1–0.5%), measurement of liquid physical properties (dynamic surface tension at 20 ms, viscosity).
Applications
- Comparative testing and classification of nozzle drift potential for manufacturers and R&D teams.
- Laboratory evaluation of spray formulations to inform low-drift product development.
- Independent test laboratories and certification bodies performing drift testing for regulatory compliance.
- Environmental risk assessment and modelling: results can be used to estimate downwind buffer distances (e.g., to protect watercourses and sensitive areas) and to select low-drift equipment for precision agriculture.
- Research into droplet behavior, spray mitigation technologies and spray application best practices.
Related Standards
- ISO 5682‑1 - Test methods for sprayer nozzles (patternator and nozzle characterization).
- ISO 25358 - Droplet-size spectra from atomizers - Measurement and classification.
ISO 22856:2008 is essential for anyone involved in spray drift testing, nozzle/manufacturer product development, regulatory testing, or environmental protection related to pesticide application.
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