The New Standard for Local Exhaust Ventilation

Professional OEHS practice always follows recognized standards of practice—codes, regulations, standards, guidelines, NIOSH-approved methods, and so on. Why? Because when we follow recognized standards of practice we give ourselves the best chance of protecting the health and well-being of workers and occupants, applying and utilizing the most cost-effective compliance approaches, and avoiding legal liabilities. (The lawyers always ask, “Did you follow the standards of practice?”)

ANSI/ASSE Z9.2-2018, , the most important standard of practice for LEV, was revised, updated, and reissued in July 2018. The 22,000-word standard is formatted in two columns: the left column presents the standard’s requirements, and the right column explains how to comply with the requirements. For the 2018 version, almost every section was revised and updated. The revision committee consisted of experts in the fields of OEHS and ventilation.  Does this standard affect you? If you are an OEHS professional, it likely does. LEV is found almost everywhere. Do you have a kitchen or cafeteria in your facilities? If you do, then LEV systems are probably there controlling ovens, dishwashers, and other kitchen equipment and operations. Do you have carpentry or metal shops? Labs? Medical facilities? Manufacturing activities? Maintenance shops? Painting facilities? Welding operations? LEV is almost always found in these locations. Also, standard requirements often refer to a “User,” a person responsible for implementing the standard’s requirements. In many cases, the User is either an OEHS professional like you and me, or a person who relies on us to assist them in complying with the standard.  Below are summaries of some important provisions of the new standard that every OEHS professional should know and follow. I have added a few comments in italics that show how and where we might be involved. Those designing, operating, maintaining, and testing LEV systems shall be qualified by training or experience to perform their jobs. . Design and operation of LEV systems shall be based on the following baseline data: emission source behavior, air behavior in the space, and worker interaction with emission sources. . LEV system designs, plans, and specifications shall be reviewed by industrial hygienists and other appropriate professionals before construction or installation begins. . Exhaust volume flowrates and equipment sizes shall be selected to dilute air contaminants to an acceptable concentration throughout the exhaust system and at the exhaust outlet or stack. . LEV systems shall be provided with performance monitoring systems. . Where tools, processes, or equipment generate different dusts, fumes, or vapors which could, if intermixed, result in a realistic health or explosion hazard, or corrosion, such contaminants shall be exhausted by separate exhaust ventilation systems. . Air exhausted through an LEV system shall be replaced by a replacement air system. The intake for the makeup air system shall be located so as to prevent the uptake of contaminants from exhaust systems, process vents, or other contaminant sources. .

Exhaust hoods shall be selected, designed, constructed, operated, and maintained to provide control of routine and anticipated emissions.  Exhaust air flowrate selection shall be determined by capture, containment, and airflow requirements. Exhaust hoods shall be equipped with continuous airflow monitoring systems, procedures, or devices.  Before routine use begins, exhaust hood performance shall be tested to assure that contaminant capture and containment performance meets the User’s requirements.