When flammable liquids or gases are released in confined spaces, vapor ignition can cause explosions resulting in fatalities, injuries, and extensive property damage. Yet Process Hazard Analyses (PHAs) and Quantitative Risk Assessments (QRAs) often fail to account for these hazards, leaving critical risks unmitigated. This research develops quantitative methods to evaluate confined explosion hazards and standardize their inclusion in PHAs and QRAs. A lessons-learned analysis of U.S. Chemical Safety Board (CSB) incidents from 1998–2025 highlights the need for improved modeling, enhanced regulatory oversight, and better integration of confined explosion assessments to safeguard workers, facilities, and communities.