Air Cleaning

Air-cleaning systems for laboratory exhaust systems, where required, shall be designed or specified by a responsible person to ensure that air-cleaning systems will meet the performance criteria necessary for regulatory compliance. See Chapter 14 of the ASHRAE 1997 Handbook of Fundamentals.


The flow rate through the filters shall be maintained at design specifications and shall not exceed the rated flow capacity of the filters.


Adsorption or other filtration media used for the collection or retention of gases and vapors shall be specified for a limited use. Specific hazardous materials to be collected, airflow rate, temperature, and other relevant physical properties of the system shall be incorporated into the selection of filtration media.


A reliable and adequately sensitive monitoring system shall be utilized to indicate adsorbent breakthrough, when such technology exists. The sensitivity of the monitoring system shall be a predetermined fraction of the Threshold Limit Value (TLV®) or appropriate alternative health standard of the contaminant being adsorbed, but shall not be more than 25% of the TLV®. The campus EH&S organization shall designate alternative health standards, if used.


The breakthrough time of the contaminant, before the effluent reaches no more then 50% of the TLV®, shall be sufficient, based upon system capacity design to allow a work operation shutdown or switch-over to a parallel air cleaner, thus providing a fresh air cleaner.


For toxic gases and vapors, the filtration system shall be designed and sized for capacity to ensure adequate collection and retention for a worst-case scenario; when in the event of a spill or other major release, adequate warning is provided for personnel to stop work or enact other emergency procedures.


Exhaust streams conveying radioactive particulate materials shall be equipped with HEPA filters that meet DOE-STD-3020-2004 specifications if potential emissions of radioactive or highly toxic particulate chemical materials are deemed to present a hazard. The filters should be installed in bag-out housings meeting the requirements of Section HA of ASME AG-1 before being connected to a centralized exhaust system. These housings should be installed with built-in challenge aerosol injection ports as well as up- and downstream challenge aerosol sampling sections. Biological exhaust hoods shall be equipped with HEPA filters to remove all hazardous biological substances prior to connection to a centralized exhaust system. Biological Safety Cabinets use filters complying with NSF-49 and IEST-RP- CC001.3, Type C requirements, while additional building HEPA filters, if used, shall meet IEST-RP- CC001.3, Type E requirements.


HEPA filters shall be protected by prefilters to avoid the cost and hazards associated with frequent replacement.


HEPA filters shall be designed and installed in a manner that allows for safely testing and replacing them. Designers must take into account ease of access, human factors, safe PM SOPs and containment of contaminants in old HEPA filters while being tested, certified and replaced. HEPA filters used to remove radioactive or highly toxic particulate chemical materials shall be installed in a manner that allows them to be quantitatively tested in accordance with Section TA of ASME AG-1 by means of a filter housing with built-in test sections, or designing the system in accordance with principles set forth in Section 5 of UCRL-AR-133354, Rev.2. Biological filters other than those installed in biological safety cabinets shall be installed so they can be tested in accordance with IEST-RP-CC034.1.


Section of ANSI Z9.5 requires that exhaust streams be “adequately filtered” for ducts conveying radioactive or biological materials before entering a combined system. Highly hazardous aerosols are customarily removed by HEPA filters. References to HEPA filter standards are given to implement this requirement of ANSI Z9.5. HEPA filters need to meet established standards and be placed in housings or systems that allow for reproducible and quantitative leak testing in accordance with recognized standards. HEPA filters for radioactive material service are often replaced using “bag-in/bag-out” methods, while biological filters are customarily vapor-sterilized before replacement. The quantitative testability requirements do not apply if there are additional HEPA filters downstream of these filters, but do apply to the last filter or pair of filters in any ventilation system equipped with HEPA filters used to protect workers, the public, or the environment.


8 CCR for chemical and biological exposures

17 CCR for radiation exposures