Filtering Hoods

By James Blount, AIA, LEED AP

For centuries inventors, researchers and scientists have been exhausting smoke, chemical fumes and other hazardous materials into the atmosphere with little concern for health, environment, or energy costs.

During the past two decades, this practice has become a major focus for building owners, scientists, lab designers, and the fume hood industry, with increased anxiety over the health and safety of laboratory workers, the impact on the environment, and escalating energy costs. Until fairly recently, many fume hoods offered little in the way of energy efficiency. For years, the basic objective of the fume hood was to capture, contain, and exhaust hazardous vapors and particulates away from the laboratory environment.

With scientific and medical research, environmental sensitivities, and energy costs all on the rise, we need to recalibrate the way we think about lab environments and forge ahead with new strategies and technologies that offer the possibilities of safe and more sustainable high-performance laboratory buildings.

This article will review current fume hood practice, as well as emerging trends in light of these considerations. It is time for us to start living, and designing our facilities, more wisely. Today’s state of affairs has presented us with the opportunity to examine the rationale behind “industrial standard practices” and “rules of thumb” and evaluate if they still have value.

CV, advanced and ductless hoods and systems

Chemical fume hoods are one of the largest consumers of energy within a laboratory building, release hazardous chemicals into the environment and, from the laboratory planning perspective, are inherently inflexible. Fume hoods are, however, an essential component of today’s laboratory.

The constant volume by-pass (CV) fume hood has been the work-horse of the teaching and research laboratory for decades, providing varying levels of fume capture, containment and laboratory safety. High-performance (“low flow”) and restricted-sash-opening hoods were developed during the past 10 years in an effort to make hood operation more economical while preserving safety. Ductless hoods with activated carbon and HEPA filters have also been gaining ground in the marketplace.

Filtering fume hoods

A recent improvement to the ductless chemical fume hood is the filtering fume hood. Dubbed by some in the industry as the next generation of chemical fume hoods, the hood incorporates new air filtration technology, universal sensor technology, and communication detection software. The new filtering fume hood has generated much excitement coupled with cautious optimism from building owners, scientists and lab planners looking for a safe and sustainable solution to the laboratory fume hood requirement.

The GreenFumeHood developed by ERLAB® of Rowley, MA, with technology now licensed to three US Companies including Air Master Systems of Muskegon, MI, incorporates a series of modular filtration columns that clean the air drawn from the hood chamber then re-circulate the filtered air back into the laboratory. Enabled by a new filtration technology called “Neutrodine®,” the filters employ a chemical process called “adsorption” and are capable of containing a much wider spectrum of chemicals than their carbon and HEPA-filtering predecessors. The filter system design incorporates a primary and secondary filter along with integrated sensor technology to ensure proper containment, alarm, notification and laboratory safety. The hood has communication software capable of providing remote management and access to the scientists, EH&S personnel, and facilities managers. Once the filter has reached its useable life, it is removed and disposed of in a controlled manner.

ERLAB’s team of scientists has invented the filtering hood in response to criticisms of ductless fume hoods. Stephan Hauville says, “The proprietary Neutrodine filtration is a single adsorbent media that doesn’t use traditional catalysts. This makes it possible to use it with hundreds of different chemicals and with the same media.”

While the ERLAB hood is not available in the U.S., the proprietary “GFH® technology” including the air filtration, dual sensors, and communication detection software, is available through an industry partnership with three US companies. Air Master Systems Corp. from Muskegon , Michigan is one of ERLAB’s partners. Air Master Systems has passed the ASHRAE 110-1995 containment test, with the GFH technology incorporated into unique fume hood chassis designs.

AMS’s “Green Solution Hood” was specifically designed to incorporate the filtering technology. Darryl Coenen, Director of Sales and Marketing, says, “What separates our Green Solution Hood from others is the AMS approach to hood design and detail. The hoods have been customized to provide optimum capture and containment, including interior posts with radius edges, down-angled front edge work surface, and sloping sash panel. Also, our hood has been designed with a patent pending spring-type sash system incorporated on the front of the hood, leaving the back wall unencumbered and allowing more natural light into the hood.”

Advantages of filtering hoods

Filtering fume hoods have several advantages over conventional ducted hoods.

  • Lower first cost. With reduced need for roof mounted exhaust fans, miles of ductwork, and complex mechanical systems, the filtering hood provides a significantly lower first cost savings.
  • Energy rebates. Equipment cost rebate programs are available from some local and national utility companies, providing rebates up to 70% of the difference in cost between a ducted and filtering fume hood.
  • Energy cost savings. The filtering hood exhaust is cleaned and circulated back into the lab, and not expelled to the exterior; the energy cost savings and environmental benefits are significant.
  • Environmental benefits. Hazardous chemical fumes and particulates are captured and contained within the filter, collected and then disposed of in an environmentally sound manner.
  • Adaptable and flexible. When installed with quick-connect laboratory utility fittings, the filtering fume hood is inherently flexible and capable of being easily repositioned throughout the laboratory without the need for time consuming and expensive construction.

Disadvantages of filtering hoods

The new Neutrodine-enabled GFH technology is new to the hood industry. As with most emerging technology, skepticism will persist until a history of successful applications can be attained. While the new technology has been installed in only a few locations in the U.S. and by all accounts is working as designed, many leading institutions and corporations surveyed in the U.S. remain hesitant, until a successful track record of use has been established. Concerns include the following:

  • Filter breach. Due to the nature of the filtering and re-circulating systems, filter failure could result in contaminated air being recirculated into the laboratory environment. To address these concerns, the new filter banks have been designed with a primary and secondary back-up filter. Integrated dual sensors capable of detecting a primary or secondary filter breach have been located down-wind from each filter and above the sash opening. If a leak is detected, the hood will go into alarm, and electronically notify the proper personnel.
  • Proper application. While the Neutrodine filter is a significant improvement, the filter cannot be used for every application and process. Due to the limitations of this technology and unpredictable nature of science research, a clear understanding of laboratory process, chemical use and the equipment is essential to ensure proper use of this equipment.
  • Maintenance. The active life of filters and sensors is tracked by the Microsoft® interface to provide service notification to a qualified lab technician, lab manager or building maintenance personnel. The filter cartridges have a minimum recommended lifespan of 24 months, and the dual sensors need to be replaced every 24 months. The filter cartridges and sensors require no special skills or qualifications to replace. However, due to the material contained within the filters, they need to be disposed of as hazardous waste and incinerated at a cost of about $30 per cartridge.

Potential applications

At this time, filtering fume hoods are not intended to completely replace ducted hoods. The limitations of this technology need to be recognized to plan proper use. Under the right conditions, filtering fume hoods can be employed in a wide range of laboratory uses.

Instructional laboratories in K-12 and undergraduate programs commonly use smaller quantities of chemicals, and less hazardous chemicals, than those typically found in pure research environments. The pattern of hood use (hours used, chemical types/quantities) within teaching labs is usually predictable and repetitive, making this lab type particularly suitable for the use of filtering technology.

While the overall level of experience of the hood users in this lab type is low, teaching labs are usually highly supervised and managed by experienced laboratory technicians. Depending on institutional policies, the lab technician could be trained and could be made responsible for the proper use, maintenance and safety of the filtering hoods. The high level of flexibility inherent with the filtering fume hoods provide these lab types a much higher level of adaptability to accommodate changing instructional needs.

In the non-teaching research environment, procedures within cell molecular biology and biochemistry research labs often result in the use of small amounts of less hazardous chemicals. Combined with benign processes, such as cultures and fermentations yielding odorant fumes, or organic purification, these applications could be a strong candidate for filtering hoods.

Organic chemistry is one of the most fume hood-intensive scientific disciplines. Within a typical organic chemistry lab it is not uncommon to have one 8-ft hood per scientist, resulting in hundreds of hoods for an average-size building. Chemical purifications and reactions represent a large component of the work regularly performed by chemists. Depending on which chemicals are being exhausted, filtering hoods could be considered. In addition to chemical processes, many pieces of equipment and solvent purification stations that require exhaust could be accommodated in a filtering hood.

Engineering labs often require the use of hood exhaust for procedures that use smelly adhesives, contain volatile compounds and create smoke from smoldering. It is within these high-density fume hood labs where the greatest potential for energy savings can be found.

Although the Neutrodine filtering fume hood technology can be applied in research, QC, teaching labs and medical labs, painstaking programming will be required. Lab planners will need to take a more comprehensive approach to documenting the chemical identities and quantities being used in order to predict the energy savings payback of the media.

Research programs for which the types and quantities of chemicals cannot be clearly defined may not be a good application for filtration.

At this time, the Neutrodine filtration technology has been tested in accordance to the protocol established in the NFX 15-211 ductless fume hood standard and approved for use with over 800 chemicals. However, even though this accounts for 99% of the typical chemical usage in labs, it does not account for all chemicals used in the scientific research processes. More specifically, this filter technology is not recommended for use in processes such as high-volume solvent distillations, extreme procedures such as boiling acid baths, or for use with deadly reagents such as cyanide. Additionally, the filter media’s efficiency could be compromised if the fume hood environment’s relative humidity exceeds 85%.

Before planning this new technology for any type of laboratory, building owners, facility managers, scientists and lab planners should first enlist the technical support from Erlab or one of their industry partners. ERLAB and Air Master Systems can assist any client before design begins and make sure the technology is suitable for the desired application.

Summary

The vision of an inherently flexible, universally adaptable, carbon-neutral laboratory is one step closer to reality as the enhanced filtering fume hood offers a glimpse into the future of what could be a truly sustainable and revolutionary lab planning trend. However, until filtration technology is developed to safely and efficiently capture, filter and contain an unlimited array of chemical mixtures, conventionally ducted fume hoods will be a part of the laboratory landscape.

It seems safe to assume in the meantime that the enormous benefits inherent in the filtering fume hood will drive not only the improvement of filtration technology, but the gradual acceptance of this approach by hood users in industry and academe. This revolution will be expedited if we collectively embrace the idea of change and think about how we can and should incorporate new and greener technologies and practices in our labs.

James V. Blount, AIA, LEED AP, is a laboratory planning architect and associate principal at Ellenzweig, Boston, a 70-person architecture and planning firm with a focus on science teaching and research facilities for academic and corporate institutions (www.ellenzweig.com).