Ferrous fan blades shall only be used for fans located within the ductwork and through which hazardous materials are exhausted.

The statement regarding the use of ferrous fan blades is deemed false because ferrous materials, which contain iron, are typically susceptible to corrosion when exposed to hazardous substances. This can lead to the deterioration of the fan blades over time, potentially compromising the efficiency and safety of the system. For fans that will handle hazardous materials, non-ferrous blades are generally preferred as they are better suited to withstand corrosive environments and reduce the risk of contamination.

While there may be specific conditions under which ferrous fan blades could be appropriate, such as in controlled environments with minimal exposure to corrosive materials, the general rule is to avoid their use in applications that involve hazardous materials. This is particularly important in ensuring both the safety and reliability of HVAC systems handling such materials. Options suggesting limited circumstance or dependence on material types bring in unnecessary complexity that is not aligned with standard practice for safety in HVAC systems.