LERAP Equipment Accreditation

Procedures for the submission and review of data packages and the awarding of LERAP-low drift star rating for ground based arable crop sprayers


An important feature of the Local Environmental Risk Assessments for Pesticides (LERAP) requirements relates to the ability to reduce the width of a buffer zone defined to protect surface water from contamination by plant protection products when the results from a local risk assessment indicate that it is safe to do so. One of the factors that is taken into account as part of the LERAP assessment is the use of technical (operational and engineering) controls to reduce the amount of spray drift produced during application that would deposit within the local environment.

Spray application systems that have been shown to have such a drift reducing characteristic will be awarded a 'LERAP-Low Drift Star Rating' which can then be used in the local drift risk assessment procedures.

There are procedures that need to be followed by those offering to supply spraying equipment for use in the UK, and for which they wish to gain a ‘LERAP-Low Drift Star Rating’ under the arrangements relating to the LERAP scheme. These are outlined below.


LERAP-Low Drift Star Ratings will be awarded to:

  • complete boom spraying systems ('sprayers') designed for operation over arable field crops;
  • nozzles or other spray generation systems ('spray generators') designed for use on boom sprayers.

Star ratings will be awarded by comparing the levels of drift from candidate sprayers or spray generators with corresponding drift levels from a reference system. This reference system shall be defined as an open structured boom construction fitted with F110/1.2/3.0 nozzles, manufactured from stainless steel, operating with a nozzle height above the target of 0.5 m.

The reference sprayer will have the same nozzle specification along the whole length of the boom ie no special nozzle design will be used at the end of the boom.

The reference sprayer shall be fitted with a boom suspension arrangement to provide isolation from both the rolling and yawing motions of the spray vehicle. Reference performance will be based on spraying of water and of a 0.1% solution of a non-ionic surfactant.

Star ratings will be awarded based on the criteria defined below.

Terminology and Drift Performance (measurable as ground deposit)

  • No LERAP-Low drift rating
    Drift levels greater than75% of that from reference system.
  • LERAP-Low Drift - one star *
    Drift levels greater than 50% and up to 75% of that from reference system.
  • LERAP-Low Drift - two star **
    Drift levels greater than 25% and up to 50% of that from reference system.
  • LERAP-Low Drift - three star ***
    Drift levels up to 25% of that from reference system.

Data Requirements

Applications for LERAP-Low Drift Star Ratings relating to either complete sprayers or spray generators will require the submission of a data package that must include:

  1. a full technical description of the sprayer or spray generation system for which a LERAP-Low Drift Star Rating is to be claimed
  2. a definition of the operational settings and conditions (or ranges within an operational envelope) within which a LERAP-Low Drift Star Rating is to be claimed together with evidence of written instructions to operators as to how such settings shall be achieved
  3. evidence to show the level of drift reduction that can be achieved with the sprayer or spray generation systems in comparison with that of the reference system

This evidence should comprise of results from a series of field tests (for complete sprayers and spray generation systems) or wind tunnel measurements (for spray generators) specifically designed to provide data for a LERAP-Low Drift Star Rating as part of the LERAP scheme.

Determination of spray deposition from nozzles or other spray generation systems (spray generators)

Protocols have been developed for sampling the sedimenting spray from both static and moving nozzles in wind tunnel conditions. For further information contact an accredited laboratory.

Data can be generated using such protocols with details of the measurement method being fully reported with the test results. Results from such tests must report a minimum of:

  1. the measured downwind spray deposits collected at three separate distances between 2.0 and 6.0 m from the edge of the spray pattern from the spray generator(s), using collectors positioned at a defined distance below the spray release height, designed to sample sedimenting spray drift.
  2. a description of the wind tunnel arrangement and sampling systems used including:
    • details of the spray generator mounting
    • a description of the airflow conditions including the mean wind speed at spray generator height
    • a description of the position and dimensions of the spray sampling system
    • details of the tracing techniques used
    • the floor conditions onto which the spray generator was spraying
    • the sampling periods and methods of controlling spray generator output
  3. data as in (a) and (b) above for both the candidate spray generator system and a nozzle representative of the reference system.
  4. evidence to validate the experimental procedures used including:
    • the calibration of control and monitoring equipment used to measure/control nozzle operating pressures, flow rates and wind tunnel air speeds
    • the recovery and stability of the tracing system used

The UK reference spraying system for wind tunnel tests is given in the table below.

Boom height 0.5 m above target (crop or ground)
Spraying speed 8 km/h
Nozzle Teejet TP 110 03
Pressure 3.0 bar
Flow rate per nozzle 1.175 L/min
Nozzle spacing 0.5 m

Determination of spray deposition from field measurements (complete sprayers or spray generators)

Measurement of spray drift in the field requires expertise and specialist equipment. It is therefore recommended that expert help should be sought in advance of conducting such experiments.

The protocol needs to reflect the equipment, application methodology and situation of use and therefore cannot be prescribed in detail in advance. However, any protocol must contain the following elements:

  • use of an appropriate reference system
  • sufficient replication
  • adequate quality checks
  • measurements at a number of downwind distances
  • appropriate environmental conditions, including wind speed
  • appropriately characterised and identified equipment for application of the test substance and measurement of environmental conditions
  • appropriately validated methods of analysis

International Standard ISO22866:2005 provides a good basis for spray drift trials. This was developed primarily for boom sprayers, but it also includes elements specific to orchard air blast sprayers. The same principles should apply to all spraying equipment, with appropriate modifications.

There are some specific differences between the ISO standard and the UK requirements, outlined below.

  1. the size of the sprayed area is more flexible than that outlined in section 3.3 of ISO22866:2005. The sprayed area should be identical for both reference and test systems. For a boom sprayer, a single track with boom width between 12 m and 36 m is generally acceptable
  2. the relative direction of sprayer and wind for the test equipment is not necessarily fixed as 90° although this is the norm and has significant advantages
  3. a confidence interval as described in section 3.6 in ISO22866:2005 may not be achievable, but it should be noted that the variability of the data can influence the level of drift reduction that can be claimed
  4. measurement of temperature difference between two heights is usually not necessary
  5. measurements of airborne spray are not required. Data relating to ground deposits only are needed
  6. a wide range of different ground collectors can be used, and the selection and handling of these is detailed in Annex D of ISO22866:2005. Data collected using water sensitive papers are unsatisfactory for this purpose
  7. measurements should usually be made at a minimum of four distances, including 2 m, 5 m, and 20 m for a boom sprayer and 5 – 20 m for an air blast sprayer
  8. some replication is required. As a minimum, three replicate runs with three measurements at each location are likely to be needed for both test and reference systems
  9. some data with a wind speed in the range 2 – 3 m/s at 2.0 m height would be ideal to include

Those submitting data packages to obtain LERAP-Low Drift Star Ratings are encouraged to submit as much relevant information as possible to enable an accurate definition of downwind drift profiles for both candidate and reference spraying systems.

How to make an application

Applications for LERAP-Low Drift Star Ratings relating to either complete sprayers or spray generators can be submitted to a laboratory accredited by HSE for the purposes of reviewing drift data. There is currently one laboratory accredited for such work:

Silsoe Spray Applications Unit Ltd
Building 42, Wrest Park, Silsoe, Bedford, MK45 4HP
Telephone: 01525 306810

Submission of data package
Dr M C Butler Ellis
Head of Silsoe Spray Applications Unit
[email protected]
Telephone: 01525 306811

Other laboratories may apply to HSE for accreditation by demonstrating that they have sufficient expertise and resource to conduct the required assessments.

Details of the submission requirement and costings can be found on the Silsoe Spray Applications Unit website (ssau.co.uk).

We recommend contacting SSAU to provide general advice relating to assessment of spray drift in support of the LERAP review process prior to any submission.

On completion of a review, the accredited laboratory will submit a report to the HSE who will consider the recommendation and award the LERAP-Low Drift Star Rating as appropriate. A formal covering letter will be sent by HSE to the organisation submitting the data package with a list of the awarded LERAP-Low Drift Star equipment ratings. Listings of the equipment and corresponding LERAP-Low Drift Star Ratings will be published on the HSE Equipment Search (pesticides.gov.uk).

Any organisation submitting a data package for review and that is not satisfied with the outcome must first discuss the reasons for any dissatisfaction with the accredited laboratory to which the data was submitted. If the reasons for the dissatisfaction cannot be resolved then a joint meeting will be held involving those submitting the data package, representatives of the accredited laboratory and HSE.

Accredited laboratories will maintain records of data packages submitted for review and these records will be available for inspection by representatives of HSE and by any third party subject to conditions of:

  • confidentiality;
  • data ownership.

Once a LERAP-Low Drift Star Rating has been awarded to a sprayer or spray generation system then it will remain in perpetuity as long as the equipment or operational specification does not change.

Notification of amendments to any equipment or operational specification already having LERAP-Low Drift status must be submitted to the accredited laboratory which evaluated the original data concerned. That laboratory will consider those changes and confirm any impact on star rating accreditation.

Further information

Is this page useful?

Updated 2023-06-01->