ISO 28139:2019 — Equipment for Crop Protection — Knapsack Engine-Driven Airblast Sprayers

1. Scope and Importance of ISO 28139:2019

ISO 28139:2019 specifies safety and environmental requirements and test methods for knapsack combustion engine-driven airblast sprayers used in crop protection. These portable machines are widely used in agriculture and forestry for applying pesticides, herbicides, and fertilizers in terrains inaccessible to vehicle-mounted sprayers, such as steep slopes, dense plantations, and smallholder farms in developing regions. This second edition supersedes both ISO 28139:2009 and ISO 10988:2011, adding comprehensive environmental requirements including droplet size control to minimize drift, residual liquid limits, and updated safety provisions reflecting current technology. The standard was prepared by ISO/TC 23 Tractors and machinery for agriculture and forestry, Subcommittee SC 6 Equipment for crop protection.

The standard covers the complete product lifecycle: design specifications, construction requirements, performance testing, and information for use including instruction handbooks and warnings. It addresses all significant hazards associated with these machines as identified in Annex A, including mechanical, thermal, vibration, noise, and chemical hazards. The standard has been updated to reflect the latest understanding of operator safety and environmental protection in crop protection applications.

This second edition supersedes both ISO 28139:2009 and ISO 10988:2011, adding comprehensive environmental requirements and updating the standard to reflect the current state of the art in sprayer technology.

2. Key Safety Requirements for Operator Protection

The standard addresses numerous safety aspects critical for protecting operators during sprayer operation in demanding field conditions, covering mechanical, thermal, vibration, noise, electrical, and chemical hazards:

Safety Requirement	Specification	Verification Method
Stability during operation	Must maintain stability on defined slopes without tipping	Stability test per Annex C
Exhaust system	Properly positioned to prevent burns and operator exposure to exhaust gases	Temperature measurement and positioning inspection
Controls	Throttle trigger, engine stopping device, liquid shut-off valve all clearly marked and accessible	Functional testing
Harness system	Adequate load distribution with absorbent carrying straps	Visual inspection plus absorbency test
Hot parts protection	Guards fitted to prevent accidental contact with hot surfaces	Temperature measurement of accessible surfaces
Vibration	Reduction by design at source, measured per ISO 20643	Accelerometer measurement at handles
Noise	Sound power level limits, reduction by design	Sound level meter per ISO 3744
Electromagnetic immunity	Must operate correctly in typical agricultural EM environments	Immunity testing per relevant standards

Operator safety is paramount: the standard mandates that ignition circuit components must be adequately insulated and that the engine stopping device must be clearly identifiable and easily accessible, with the stop function clearly marked. The vibration measurement must account for both handles.

3. Environmental Requirements and Test Methods

A major addition in this edition is the comprehensive set of environmental requirements aimed at reducing ecological impact. Droplet size control is critical: the sprayer must produce appropriately sized droplets to minimize off-target drift while maintaining effective crop coverage. Spray tank specifications include strainers and filters to prevent nozzle clogging, a contents gauge for liquid level indication, and limits on total residual liquid after emptying to minimize chemical waste. The fan must provide sufficient air velocity for proper droplet transport, measured using a defined sampling grid per Annex B. The carrying strap material must not absorb excessive pesticides, reducing operator exposure during extended use. Chemical hoses must withstand operating pressures without leakage.

Environmental Parameter	Requirement	Purpose
Droplet size distribution	Controlled to minimize drift	Reduce environmental contamination
Carrying strap absorbency	Must not absorb excessive pesticide liquid	Reduce operator dermal exposure
Spray tank material	Resistant to agrochemical attack	Prevent leaks, ensure durability
Total residual liquid	Minimized after emptying	Reduce chemical waste disposal
Chemical hoses	Pressure-rated, leak-proof connections	Prevent operator contact

Droplet Size Classification

The standard references established droplet size classification categories used in crop protection. Proper droplet size selection depends on the target crop, pesticide type, and environmental conditions. The classification system helps operators choose appropriate nozzles and operating parameters:

Category	VMD Range (micrometers)	Typical Application
Very Fine (VF)	< 100	Fungicides, insecticides requiring thorough coverage
Fine (F)	100 – 175	Contact herbicides, thorough canopy penetration
Medium (M)	175 – 250	Systemic herbicides, broadleaf weed control
Coarse (C)	250 – 375	Pre-emergence herbicides, drift-sensitive areas
Very Coarse (VC)	> 375	Soil-applied herbicides, maximum drift reduction

The fan speed, liquid pressure, and nozzle type all influence the resulting droplet size distribution. Manufacturers must provide clear guidance on achievable droplet size ranges for their equipment under various operating conditions, enabling operators to make informed choices for each application scenario.

Engineering Design Insights

For manufacturers, achieving ISO 28139 compliance requires a holistic engineering approach. The stringent vibration requirements demand carefully designed engine mounting systems with appropriate isolation. The exhaust system must balance noise reduction against backpressure constraints that affect engine performance. The harness system requires both extended-wear comfort and resistance to pesticide absorption, typically achieved through multi-layer fabric construction with chemical-resistant coatings. The liquid handling system needs leak-proof connections throughout, with chemically resistant materials such as polypropylene or stainless steel for wetted components. Modern designs increasingly incorporate electronic engine management for consistent performance and lower emissions. The fan system design is particularly critical: it must generate sufficient air velocity for adequate droplet transport while minimizing energy consumption and maintaining acceptable noise levels. Computational fluid dynamics (CFD) simulation is increasingly used during development to optimize the air duct geometry and nozzle placement for uniform spray distribution patterns.

The inclusion of comprehensive environmental requirements in this standard represents the industry’s commitment to reducing pesticide drift and environmental contamination while maintaining effective crop protection capabilities.

4. FAQs

Q: What types of sprayers are covered by ISO 28139?
A: It covers knapsack combustion engine-driven airblast sprayers only. Electric or battery-powered sprayers are not within scope and may be covered by other standards.

Q: How is droplet size measured for compliance?
A: Droplet size is determined through standardized test methods using laser diffraction or other suitable measurement techniques as specified in the environmental test provisions.

Q: What information must the instruction handbook contain?
A: Technical data including engine power, tank capacity, weight, noise and vibration values; operating instructions; maintenance schedules; safety precautions; and environmental protection guidance.

Q: What are the main changes from the 2009 edition to the 2019 edition?
A: The 2019 edition adds environmental requirements and tests, updates safety requirements to current technology, and excludes ergonomics which is now covered by separate standards.