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Tablets & Capsules March 2017 39 tion with the normal risk assessment and hazard analysis that precede equipment selection. Combustible dust con- trol is one area of concern. As part of the upfront analysis, your dust should undergo explosibility testing to determine its combustible and explosive properties. Explosibility test- ing is essential to analyzing which type of dust collection system is best for a specific application. It will also inform your selection of the explosion protection/prevention devices needed in order to comply with applicable NFPA standards. Figure 4 shows a rendering of a dust collector equipped with explosion suppression equipment. Where containment risks are a concern, you should also consider surrogate testing. Surrogate testing of con- tained dust collection equipment—when performed under controlled parameters using a surrogate that mim- ics the particle characteristics and flowability of the active pharmaceutical ingredient—is a safe and effective method to help predict how well the system will contain the process and remain in compliance with emission requirements. For best results, follow the testing protocol of ISPE's "Good Practice Guide." Many manufacturers will also need to consider thresh- old limit values, or TLVs, which are established by the American Conference of Governmental Industrial Hygienists. The other option is to use internally pre- scribed occupational exposure limits, or OELs. Both mea- sure the airborne concentration of a substance below which workers are believed to be protected while Figure 4 Dust collection system equipped with explosion suppression equipment exposed to the substance daily for 8 hours. Emissions readings from Standard 199 test reports can help you per- form a risk assessment to determine which equipment best suits your application. Until Standard 199 test reports become more widely available, it's likely that equipment specifiers will some- times continue comparing filters using MERV rankings or other efficiency ratings. Although a MERV ranking is a good indicator of a filter's initial efficiency, keep in mind that it doesn't measure pressure drop, emissions while pulsing, energy performance, or the other parameters included in Standard 199 testing. T&C References TLV/BEI Guidelines. American Conference of Governmental Industrial Hygienists, Cincinnati, OH. www.acgih.org. ANSI/ASHRAE Standard 199-2016, Method of Testing the Performance of Industrial Pulse Cleaned Dust Collectors. American Society of Heating, Air- Conditioning and Refrigeration Engineers, Atlanta, GA. www.ashrae.org. ANSI/ASHRAE Standard 52.2, Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. Assessing the Particulate Containment Performance of Pharmaceutical Equipment, 2012. International Society for Pharmaceutical Engineering (ISPE), Bethesda, MD. www.ispe.org. NFPA 652: Standard on the Fundamentals of Combustible Dust. National Fire Protection Association (NFPA), Quincy, MA. www.nfpa.org. NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. Rick Kreczmer is director of aftermarket and David Steil is pharmaceutical market manger at Camfil APC, 3505 South Airport Road, Jonesboro, AR 72401. Tel. 870 933 8048. Website: www.camfilapc.com/pharma. Further reading For more information about specifying dust collection equipment and filters, see: • Selecting a cartridge dust collection system for tablet coating operations. David Steil. April 2015. • How to ensure your dust collection system complies with combustible dust standards. David Steil, Tony Supine, and Mike Walters. May 2013. • Ten tips for selecting cartridge dust collection equip- ment for tabletting operations. David Steil. March 2012. • Dust collector filters: Calculating the total cost of own- ership. Tomm Frungillo and Tony Supine. October 2012