Regulations limit the APCD inlet to no higher than what temperature difference than was present during the most recent successful annual stack test?

The correct response indicates that regulations stipulate the APCD (Air Pollution Control Device) inlet temperature can vary by no more than 30 degrees Fahrenheit from the temperature recorded during the most recent successful annual stack test. This limit is critical in maintaining consistent performance and ensuring that emissions remain within allowable limits.

Temperature fluctuations can affect the efficiency and emission characteristics of the APCD. By restricting the temperature difference to 30 degrees Fahrenheit, regulators help ensure that the control device operates under similar conditions to those it was tested against, thus helping maintain compliance with environmental regulations. Adhering to this temperature difference minimizes the risk of increased emissions that could occur if the inlet temperature were to rise significantly beyond the tested parameters.

In the context of air quality management and environmental protection, maintaining such strict guidelines is essential to prevent potential risks associated with emissions from power generation and industrial processes.