What should be used to ensure that return air is not sourced from the engine room?

Using smokebombs is an effective method to visually determine if return air is being sourced from the engine room. When deploying smokebombs in areas near the air intakes, it helps illustrate the airflow patterns and reveals whether smoke is being drawn into the return air ducts. If smoke enters the ducts, it signifies that air from the engine room is being pulled into the HVAC system, which can pose significant safety risks due to possible contaminants or hazardous gases.

In contrast, infrared temperature guns are used to measure surface temperatures and do not provide information on airflow paths or sources of air intake. Digital multi-meters are essential for electrical diagnostics and do not play a role in air quality or sourcing. While a carbon monoxide detector is critical for monitoring toxic gas levels, it does not visually demonstrate the air movement or sourcing in the ducts, which is necessary for identifying return air issues. Thus, smokebombs serve the specific purpose of ensuring that return air is not sourced from potentially harmful areas like the engine room, making them the right choice for this scenario.