Bio Shield Tech - HVAC ANTIMICROBIAL COATING SPECIALIST. Antimicrobial surface coatings can easily be shop-applied by brush, roller, or spray techniques to ducts, drain pans, AHU’s and most HVAC system components. Silver Bullet AM® is available in Black, White and in Stainless Steel Gray. With more than a decade of industry experience, we have the insights and expertise to help you understand antimicrobial applications. We’re here to help you choose the right products and solutions required to meet your needs. We are the source for all your antimicrobial requirements.