## 2 Materials and Methods
Using extensive feedback from the PRG on multiple versions of a draft tool (41 versions), an IT specialist developed a trial version of the CHAP-Risk under the direction of the research team. **Recruit Trial Workplaces (Step 2b):** while the CHAP-Risk tool was being developed, we also undertook an extensive recruitment process to engage workplaces to trial the tool when it was ready for testing. The recruitment process was coordinated through the PRG, with the unions and health and safety associations particularly engaging with their members/stakeholders to encourage workplaces to participate in the trial. As with most workplace-based research [8,27], gaining workplace participation was difficult and recruit  
Figure 1: CHAP-Risk development process steps. ment activities relied substantially on personal contact and networking. Six workplaces (two manufacturing companies and four municipalities) agreed to trial the CHAP-Risk tool. **Pre-trial Evaluation/Orientation Meetings (Step 3):** an initial (virtual) meeting was scheduled with each workplace. These meetings were conducted to provide an overview of the project and allowed the research team to gain an understanding of the workplace and how they operated, including what types of chemicals they used, what were their current approaches to chemical management and WHMIS training, and to understand the role of the WHSC in the workplace. These meetings were recorded and transcribed and attended by the OHS leader and members of the WHSC. The outcomes of these meetings assisted the research team in designing the training, trial and evaluation steps of this study. **Training (Step 4):** each workplace received training on how to use the CHAP-Risk tool and how CHAP-Risk could support the workplaces' existing approach to chemical management. This training was conducted virtually (via Zoom) to groups of workers and consisted of a presentation, a demonstration of CHAP-Risk, and a question-and-answer session. Each workplace was then provided with a link to resources which were needed for the trial. **Workplace Trial (Step 5):** workplaces trialed the latest version of the CHAP-Risk tool over the next month to assess the health and safety risk of a set of chemicals they were currently using. One of the workplaces used the tool to assess more than a hundred of their chemicals, while others evaluated the tool using ten chemicals. As this was an iterative process, workplaces/participants gave feedback on different versions of the tool, i.e., feedback from initial workplaces was incorporated into newer versions of the tool, so that as the study progressed, workplaces using the tool in the later part of the trial used more updated versions of the tool. **Post-Trial Evaluation (Step 6):** the 'usability' and 'utility' of the CHAP-Risk tool (and the training program) was evaluated through focus group interviews to gain a deeper insight into user experiences. All evaluation sessions were undertaken online through Zoom with the sessions recorded and detailed notes taken of the discussion. Participants were also able to provide 'private' feedback via the chat function on zoom. Some participants sent individual emails with their feedback. The recordings, chat-notes and written feedback were transcribed and analyzed using standard qualitative methods [28] that investigated dominant themes and trends. This involved the displaying of data in meta-matrices which were shared with three members of the research team, enabling verification of the data. This matrix-based, conceptual-model-guided, synthesis process ensured that comments were aggregated and anonymized. The matrix allows for a visual representation of how the themes were derived from the text, and how themes helped capture the participants comments on usability and utility of the CHAP-Risk tool. This process also enabled strong themes (i.e., those mentioned by many participants) and weak themes (those mentioned by one person) to emerge. The addition of both strong and weak themes is a variation from the standard analysis method.