Skip to main content

Impactor Group


  • Share and build scientific knowledge and best practises using impactors for characterizing pharmaceutical aerosols.
  • Ensure robust, fit-for-purpose and science-based impactor methods are implemented in pharmacopoeias.
  • Ensure harmonization within the impactor area.
  • Work with manufacturers in-line with the above objectives.

Latest Impactor News:

Impactor Quality Control: How to set NECESSARY and SUFFICIENT Quality Standards on Impactors used for Batch Release testing

The Impactor sub-team have published several articles on this topic and have shared them here.

Roberts, D. L. and Mitchell, J. P. (2019) ‘Measurement of Aerodynamic Particle Size Distribution of Orally Inhaled Products by Cascade Impactor: How to Let the Product Specification Drive the Quality Requirements of the Cascade Impactor’, AAPS PharmSciTech. AAPS PharmSciTech, 20(2), pp. 1–10. doi: 10.1208/s12249-018-1276-9

Appeared in Inhalation, Aug 2019

Appeared in Inhalation, Dec 2019

Appeared in Inhalation, Dec 2020


Applied Particle Principles
University of Loughborough
GSK (Leader)
Independent Consultant
University of Hertfordshire

Work plan

New projects and teams have been set up at the beginning of 2015. These have been updated following a 2018 review. Below is a list of projects selected. Projects are either in their infancy due to the new organisation of work in the Impactor Sub Group or work is being consolidated from previous work to generate a more refined objective and plan for the future.


Calibration of Impactors

  • Objective:
    To provide options for industry to calibrate impactors in an effective manner.
  • Status:
    Project initiated. To support this activity it was suggested that impactor group participants should contribute towards a photo library of typical issues observed with failing/defective impactors. The impactor group could then collate a failure log for impactors to help identify common failure modes.

Good CI practices (GCIP) / variability in CI testing

  • Objective:
    Support Pharmacopeial development of GCIP and understand sources of variability in the CI measurement process.
  • Status:
    Project initiated. Initial work has identified synergies with IPAC/RS and therefore team will ensure there is no duplication and clarity between the two efforts. The EPAG team will concentrate on supportive practical work to demonstrate GCIP/variability in CI testing and recommendations for hands on improvements. This group will also follow pharmacopeial development and updates closely to ensure robust, fit-for-purpose and science based impactor methods in pharmacopoeias. The group are in the process of discussing comments to be provided to IPAC-RS on the Good Cascade Impactor Practice Stimulus article.

Recent meeting update:

Industry Perspective on Pressure Drop Measurement (NM)

NM provided an update at work conducted at Vectura to support Darryl’s investigations, and provided an industry perspective on using ΔP measurements for in-use impactor monitoring.

Vectura are currently gathering data on their in-use NGI’s to determine whether the ΔP measurements are sensitive enough to detect atypical impactor results. They are currently awaiting mensuration of the uncleaned NGI to determine correlation of ΔP with changes in nozzle diameter.

The presentation raised the following observations:

  • JTS asked if analytical noise could mask ΔP effects? (team concluded that more data is needed to assess this)
  • CB raised the issue of whether the MOC performance could be assessed in any way
  • JM/DR commented that if shown to be useful this could form the basis of a future system suitability test

MC/DR commented that the issue of whether impactor manufacturing tolerance limits were appropriate for in-use limits. If these could be widened would ΔP be more useful?

Abbreviated Impactor Method (AIM)

  • Objective:
    To provide industry guidance on AIM opportunities
  • Status:
    Project team initiated. The previous work in this area has been consolidated and separated from the EDA. A further understanding will be sought on what companies are using as AIM and at which stage of development they see most benefit. This will allow a more focussed approach on assisting industry.

Recent meeting update:

EPAG poster presented at the conference. MH asked whether the poster constitutes the final report for this activity?
  • JM commented that that AIM is under consideration for inclusion in the Ph Eur, and is being discussed by the USP
  • HM asked whether the impactor group can recommend suitable AIM options for future effective use, and that perhaps the questionnaire data could inform this process?
  • CB commented that the AIM questionnaire has provided background information for the CFD programme and highlighted the divergent approaches in use. Everybody should be encouraged to publish available data which may help the industry to focus on a reduced number of key devices going forward
  • MC commented that AIM is probably in Wider use than our current knowledge indicates (possibly during early phase development when considered low risk)

The group took an action to gather more information regarding which devices are in use, with a view to designing a more specific questionnaire to gauge wealth of available data, and to consider circulating the questionnaire to users outside of the impactor group (Copley may be able to help with this if we decide to explore this option). The group should also consider whether a new workshop (perhaps at a future DDL?) would be useful to present new data to a wider audience.

Throats and CFD modelling

  • Objective:
    To use CFD on further understanding the mechanism by which inertial impactors work and how throats can affect the subsequent deposition profiles.
  • Status:
    Project team initiated. Work consolidated with Henk’s group at Nottingham. Excellent progress to date on CFD modelling which has linked in to explain some of the practical data generated in the air volume studies. Funding needs to be secured in this exciting area to support ongoing work that is very likely to assist in impactor use/design for the future. Publications of work have occurred with a DDL podium presentation.

Recent meeting update:

HV gave an update presentation on current CFD modelling activities to the team, as well as prompting a discussion on possible future activities.
Current Projects Report
  • HV is currently drafting a publication to cover the study of transient flow in the impactor.
  • HV provided a summary of CFD project modelling flow and particle deposition in the rNGI – Inclusion of filter at stage 3 of the impactor, induces a significant ΔP at stage 3 in steady state. Future work will study transient flow but this is complex to do.
  • Model of flow & particle deposition in FSI – HV reported successful development of transient and steady state models

Modelling of particle deposition – HV reported that Steady flow model reveals complex flow distribution in single nozzle impactor and that Collection efficiency curves can be matched to data by adjusting models of turbulence and particle restitution behaviour.

Future Studies

Four options for future work were presented, of these option 3 – Study effect of low, medium and high resistance on transient flow through cascade impactors – was preferred.