From HVAC system perspective the following pharmaceutical ra

From HVAC system perspective, the following pharmaceutical raw material form is most troublesome to clean

Solution

Heating, ventilation, and air conditioning (HVAC)^[1] is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer.

All other can be clean easily due to there conservative nature but chemicals possess reactivity and hence diffficult to clean .