What are two acceptable tools for visually assessing spillage?

The correct answer involves using tools that can effectively demonstrate the presence of spillage, particularly from gas appliances. Smoke is commonly used for visual assessments because it can clearly show the direction and presence of air movement, indicating whether there is a spillage issue. A mirror is useful for checking places that might be hard to see, such as inside a vent or flue, where spillage could occur but is not readily visible. Together, smoke and a mirror allow for a comprehensive visual assessment of the area surrounding appliance venting and can help determine if harmful gases are escaping into the living space.

The other choices, while including some relevant tools, do not pair as effectively for the specific purpose of assessing spillage. For example, a camera is typically used for documentation rather than for live assessment. Flame can indicate combustion but does not help visualize spillage in the same way smoke does. Air pressure meters measure pressure levels, which might be related to spillage but do not directly assess it visually. Similarly, a thermometer and anemometer measure temperature and air movement but do not reveal the presence of spillage in a clear visual manner.