A New Generation of Laboratory Safety: Filtered Fume Enclosures

A New Generation of Laboratory Safety: Filtered Fume Enclosures

Think Green, Think Clean, Think Mystaire®

There is a growing need for laboratory control systems that address safety, energy use, and capital savings concerns. With increasingly stringent environmental and regulatory guidelines, it is evident that safety is of great importance and cannot be compromised. Many standard laboratory procedures can result in the generation of hazardous fumes. For most laboratories in the industrial, educational, hospital, forensic, and pharmaceutical sectors, filtered fume enclosures are a vital element of the scientific operation and impact on safety. When properly operated, they control gasses, fumes, and powders. In addition, filtered fume enclosures will prevent inhalation exposure to highly toxic substances, such as carcinogens. For the pioneers of scientific research, it may have been acceptable to conduct experiments with toxins on an open bench. However, regulations now state that such experiments must be conducted in an environment that ensures efficient and safe fume containment. Ductless filtered fume enclosures address this need.

Effects of Air Velocity on Hazardous Fume Containment

For hazardous fumes to be contained, there must be sufficient, uniform air velocity or “face velocity” across the sash of the enclosure. Low Face Velocity: If set too low, you risk providing insufficient velocity to overcome the competing airflow caused by the operator moving or working in front of the fume enclosure. High Face Velocity: Too high face velocity can lead to a “roll effect,” whereby air entering the enclosure causes a vortex, sending air across the work surface, up the back, and along the top of the enclosure. The air then becomes trapped, which can lead to a dangerous escalation of contaminant levels. In some instances, the contaminated air can “roll out” of the enclosure into the operator’s breathing zone and potentially endanger other occupants within the laboratory. Not only does the roll effect have serious safety consequences, but it can also disturb delicate operations — and thus affect the final results of experiments — potentially jeopardizing years of dedicated research. A variable air volume system within a laboratory must have a fast and responsive control system to provide an effective tool to help with satisfactory fume enclosure and laboratory containment. The majority of existing filtered fume enclosure control systems use analog technology. However, analog controls do not have the flexibility to respond to dynamically changing fume enclosure and laboratory conditions. How, then, can a rapid response be guaranteed?

Going Above and Beyond for Maximum Operator Protection

Advantages of Digital Control Systems

To meet the need for rapid response times, manufacturers have engineered digital control systems to work in conjunction with ductless filtered enclosures. The advanced monitoring system on the ISOLA™ filtered chemical workstation — EverSafe™ III Touch Controller (Figure 1) — uses state-of-the-art digital sensor technology, providing highly accurate, instant readings. These readings allow the system to continuously monitor and display the active face velocity, ensuring users that they are working in safe conditions. Sophisticated sensors determine any chemical breakthrough based on the type of solvent used within the filtered enclosure. Visual and audible alarms alert operators when airflow falls below the industry recommended standard of 80 fpm, indicating, for example, an inoperative blower or loss of efficiency due to blocked filters. A second alarm sounds if filters are approaching saturation, allowing replacement well before exposure limits are reached. Additional safety features include a digital display that shows the filter type in use and the correct application of the filter, a bar graph for indication of filter saturation, and a time display to track how long the filter has been in use and its maximum time allowance. (Figure 2) Different types of research incur different risks and will, therefore, require different containment levels. Effective capture and filtration systems will also help make the laboratory environment safer from airborne contaminants.

Carbon Filtration

Carbon filtration methods combine the highest level of operator safety while protecting the environment from potentially harmful fumes. The system is based on recirculatory technology using carbon filtration to adsorb and capture harmful and toxic fumes that occur in many laboratories. After passing through a series of filters, clean air is recirculated back into the work environment instead of being vented outside, thereby reducing atmospheric pollution. There is also an added cost benefit when using ductless enclosures since there is no loss of heated or air-conditioned air. Ductless filtered fume enclosures are designed to accommodate a variety of filters that can capture a broad range of fumes and airborne particulates. In order to ensure proper filtration, it is essential to match the filter medium to the contaminants to be contained. A comprehensive range of high-efficiency filters has been developed with the ISOLA filtered chemical workstations. Contaminated air is drawn through a three-stage filter system (pre-filter, main carbon filter, plus safety filter) for maximum fume adsorption. The electrostatically charged pre-filter captures particulate down to 0.5 microns and protects the main filters from contaminants (Figure 3). A third backup safety filter offers triple the protection. Your safety is the highest priority when using any ISOLA workstations since they meet and exceed all requirements of OSHA and ANZI Z9.5 standards.

Why Carbon and When to Use It

High-capacity activated carbon and specially treated carbon filters are recommended to contain fumes and vapors, covering most applications. Although activated carbon can be manufactured from various raw materials, Mystaire exclusively uses activated carbon derived from high-grade coconut shells. High-temperature steam activation of coconut shell carbon leads to slow and controlled destruction of the solid carbon mass, producing millions of pores. It is the microporous nature that guarantees a vast internal adsorption surface. Steam-activated coconut shell carbon effectively adsorbs most commonly found organic compounds from the air, including aliphatic and aromatic hydrocarbons, solvents, organic acids, aldehydes, ketones, alcohols, esters, and many halogen and nitrogen compounds. But what about substances not physically adsorbed by activated carbon, such as lower molecular weight compounds and inorganic gasses? Where gasses are chemically reactive, specially impregnated chemisorptive carbon filters are recommended. These filters use treated carbons that combine a chemical reaction with carbon’s adsorption capacity. Compounds are broken down into various elements for easy adsorption. Adding impregnates, such as a neutralizing or oxidizing agent, enhances the adsorption rate. Consequently, an even compound with low adsorption ratings, such as ammonia, hydrogen sulfide, inorganic acid vapors, radioactive iodine, mercury vapors, and formaldehyde, can be effectively trapped onto the chemisorptive carbon filters and rendered harmless. Some activated carbon filters are impregnated to enhance adsorption. For example, there are specialized filters for sulfur compounds, where the activated carbon is impregnated with sodium sulfate to enhance chemical adsorption.

HEPA Filters

While standard filtered fume enclosure applications, such as containment of acid spillage or protection from nuisance fumes, require a pre-filter and carbon filters, high-efficiency particulate air (HEPA) filters can be used for cleanroom applications. Originally developed by the military for nuclear particle filtration, HEPA filters are specially designed air-cleaning devices that have demonstrated filtration efficiencies of 99.97% of particles greater than or equal to 0.3 microns in diameter. When used in combination with pre-filters, HEPA filters are an effective way to capture particulates of smoke, dust, fingerprinting powders, asbestos, mold spores, bacteria, and other pathogens, as well as for use with highly controlled samples in cleanrooms. ISOLA filtered workstations can combine active carbon filters with HEPA filters, enabling its customers to work with solvents in a cleanroom environment.

Conclusion

When deciding upon a suitable filtered fume enclosure for a laboratory, you should consider digital controls for face velocity, visual and audible safety alarms, and filter-to-application compatibility. A well-designed ductless filtered fume enclosure will provide a safe and effective means of containing a wide range of fumes and, where required, powders and other particulates, providing both operator and environment protection, and improving the overall efficiency of the laboratory.