What types of gases should be tested for before entering a potentially hazardous confined space?

Testing for gases before entering a potentially hazardous confined space is crucial to ensure the safety of individuals who may need to work in those environments. The correct choice emphasizes the importance of being aware of both combustible and toxic gases.

Combustible gases present a risk of fire or explosion, which can occur if there's a mixture of gas and air outside of safe limits. Toxic gases can pose serious health risks, including immediate threats to life or long-term health effects. Identifying the presence of either type of gas is essential to evaluate the risks before anyone enters the space, allowing for appropriate safety measures, such as ventilation or respiratory protection, to be put in place.

While other options mention specific gases or subsets, they do not encompass the full range of potential hazards that could be present in confined spaces. Therefore, focusing on the broader categories of combustible and toxic gases provides a comprehensive approach to safety in confined spaces.