What is a requirement for the contractor's plant site laboratory regarding windows?

The requirement that the contractor's plant site laboratory must have at least one outside door is essential for ensuring proper accessibility and safety. An outside door allows for the convenient entry and exit of personnel and materials, facilitating the smooth operation of the laboratory. This feature is crucial for maintaining efficient workflows, particularly in a setting where testing and inspections are being conducted, as it allows for quick access to emergency exits if needed.

In contrast, the other options do not fulfill the same functional or safety needs. For instance, having no windows could hinder natural ventilation and visibility, which can be important for monitoring environmental conditions and fostering a productive working environment. A view of the plant may be desirable for certain laboratorial observations, but it is not a critical requirement for the functionality of the laboratory. Tinted windows, while offering benefits such as glare reduction and temperature control, do not align with the primary structural necessity of allowing access to the laboratory. Therefore, having at least one outside door stands out as a fundamental requirement for the laboratory's design and operational practicality.