Threshold Limit Values cannot be exceeded during which of the following scenarios?

Threshold Limit Values (TLVs) are guidelines that indicate the maximum concentration of a hazardous substance that workers can be exposed to without adverse health effects. These values are intended to protect workers during typical workdays, which are often structured around eight-hour shifts.

The importance of adhering to TLVs is clear in the context of worker safety; exceeding these limits can lead to health risks. Option C emphasizes that TLVs must not be exceeded even if proper Personal Protective Equipment (PPE) is not provided, underscoring the notion that reliance on PPE should not be used as a substitute for maintaining safe exposure levels. It highlights the principle that the primary responsibility lies in ensuring that environmental concentrations remain within safe limits, regardless of personal protective measures.

In contrast, the other options may imply that extending work hours or relying solely on PPE could somehow mitigate the risk associated with exposure beyond TLVs, which is not aligned with safety best practices. Ensuring that TLVs are respected at all times is crucial for maintaining a safe working environment.