<![CDATA[Occupational Safety and Health (K3) is an important aspect in learning SMAW welding practices because it has a high risk of work accidents. Based on the results of initial observations in the Machine Workshop of SMKN 1 Tuban, it was found that many students still did not use complete Personal Protective Equipment (PPE) during practice. This study aims to develop a valid and effective risk matrix-based PPE compliance observation instrument to reduce K3 violations in SMAW welding practices. The research method used Research and Development (R&D) with the ADDIE model which includes the stages of Analysis, Design, Development, Implementation, and Evaluation. The research subjects were 37 students of class X Mechanical Engineering. The research instruments were a checklist for PPE use, work condition observation sheets, and a risk matrix. The validation results by three experts obtained an average score of 4.65 with a very valid category, while a CVR value of 1.00 indicated that all instrument indicators met the content validity criteria. The implementation results showed that the number of PPE use violations decreased from 81 to 37 violations. The average PPE use compliance score increased from 1.857 to 3.914.The Wilcoxon Signed Rank Test results showed a significance value of p < 0,001 and the N-Gain analysis obtained a value of 0.6127 with a moderate category. Thus, the risk matrix-based PPE compliance observation instrument is effective for improving OHS culture in SMAW welding practices.]]>
