Which factor does NOT necessitate the installation of "No Smoking" signs?

The factor that does not necessitate the installation of "No Smoking" signs is the presence of rooms without chemicals. In general, "No Smoking" signs are required in areas where there is a higher risk of fire or exposure to hazardous materials.

In areas where food is prepared, smoking can introduce contaminants and increase fire risks, which is why signage is appropriate. Similarly, locations where hazardous materials are used or stored have clear regulations concerning smoking due to the potential danger that an open flame or heat source could pose. For outdoor hazardous material storage, the requirement is particularly heightened within a specified proximity (25 feet), emphasizing the need for strict safety measures.

However, in rooms devoid of chemicals, there is a lower risk of fire or explosion associated with smoking, making the installation of "No Smoking" signs unnecessary in such environments. Therefore, the correct answer reflects a scenario where smoking does not inherently pose the same level of risk as it does in other specified areas.