According to the US Bureau of Labor Statistics (BLS), 882 people were killed or injured due to confined space accidents in 2011-2017. Occupational accident statistics published in 2008-2018 by the Taiwan Occupational Safety and Health Administration (OSHA, Taiwan) show that 70 people suffered from disasters and 52 were injured in the 64 accident reports involving confined spaces. In the US, on average, 126 people die each year in accidents related to confined spaces, and in Taiwan, an average of 8 people per year are casualties of accidents involving confined spaces, proving that it is an area of concern that cannot be neglected. When misjudgments occur in confined spaces, not only can people be hurt, but they can even lose their lives, and the risks associated with confined spaces can subsequently result in rescue personnel also being killed or injured. This study was conducted via the systematic causal analysis technique (SCAT), which was proposed and developed by the International Loss Control Institute (ILCI), with the intention of identifying the critical basic causes of the confined space accidents that have occurred over the years in the Taiwan area, in order to propose corresponding improvement strategies. After investigating the statistics in Taiwan, it was determined that hydrogen sulfide was involved in 45% of accidental deaths in confined spaces, followed by 11% involving carbon dioxide, 9% involving carbon monoxide, and 7% involving toluene. Additional analysis of non-standard acts identified "failure of operating procedures" as being involved in 27% of accidents, followed by 25% involving "improper personal protective equipment" and 23% involving "incorrect position". The analysis of non-standard conditions revealed that "dangerous workplace" was involved in 39% of accidents, "improper protective measures" in 30%, and "inadequate ventilation" in 27%. In accordance with our analysis results, it could be suggested that hazard prevention strategies for confined spaces, in addition to encouraging avoidance of non-standard acts by personnel, should also strive to improve these non-standard conditions. Otherwise, if not prevented deliberately and in a fundamental, relevant accidents will remain inevitable.