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Explosion-Proof Hoods
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Laminar Flow and Fume Hoods FAQs
Laboratory hoods serve a number of critical purposes in the lab environment.
Product protection from particulate contaminants in the lab environment, including microbes
Such hoods, often called laminar flow workstations or clean benches, use a flow of HEPA-filtered air to prevent influx of viable and non-viable particles into the enclosure and to sweep away any contaminants generated by the work process.
Protection of personnel and lab environment from substances generated inside the enclosure
For fume containment, laboratory fume hoods use a ducted ventilation system that maintains negative pressure. Where ducting is impractical, ductless hoods are also available for removal of non-hazardous contaminants (fumes or particles), using either HEPA or activated carbon filters.
Protection of product, operator and environment
Biological safety cabinets combine aspects of both hood types: a laminar flow of micro-filtered air and negative-pressure containment of bio-hazard fumes.
Laminar Flow Hoods
Laminar flow hoods (also called laminar flow clean benches) force air through a HEPA or ULPA filter to create a clean work area free of nearly all contaminating particulates, including bacteria, mold spores and many viruses. These hoods use a vertical or horizontal airflow design. Both provide excellent protection of products from particulates and cross-contamination, but do not protect the operator or environment.
So why choose one over the other? Vertical laminar flow hoods (VLF Hoods) require less floor space, but more overhead clearance. In addition, a sash at the front of the VLF hood provides a barrier between air exiting the hood and the operator’s face. VLF hoods create turbulent air flow when air strikes the work surface, requiring sterile work to be performed above the work surface.
HLF hoods minimize air turbulence (and particle backflow) on the work surface except where equipment disrupts the horizontal airflow. However, they direct the airflow directly at the operator’s face and require more depth to accommodate placement of the fan filter unit at the rear of the hood.
Read more about the differences between horizontal and vertical laminar flow hoods
Fume Exhaust Hoods
Laboratory fume hoods draw air from the environment through the opening of the hood, allowing environmental contaminants into the work area. Thus, lab fume hoods do not offer a sterile environment or product protection. Instead, chemical fume hoods are designed to protect the operator from dangerous or irritating fumes and powders generated from work performed inside the hood.
In ducted fume hoods and canopy fume hoods, air passes out of the hood through a duct leading to an in-house ventilation system that contains and/or neutralizes hazardous materials.
In ductless fume hoods, fans draw exhaust air through a series of filters that remove irritating substances before release back into the room. Since these filters are not 100% efficient in removing all substances, ductless fume hoods are not advised in the presence of biohazards; however, they provide a convenient, cost-effective solution for operations involving irritating but non-hazardous fumes in facilities where an in-house HVAC system cannot be accessed.
Biosafety Cabinets
Biological Safety cabinets combine design aspects of both laminar flow and fume hoods. Filtered air is directed downward onto the work surface and then travels into a plenum through openings on the front and sides of the hood. Depending on the classification of the biosafety hood, some percentage of air is recirculated through a HEPA filter while the rest is directed out of the hood through an exhaust system. Thus, biosafety cabinets offer operator, environmental and product protection.
These laboratory safety cabinets (sometimes called IV hoods or compounding hoods) are ideal when preparing sterile medications such as chemotherapeutic agents that may pose a risk to the operator.
BSCs, BSLs, and ISO Classes
When it comes to working with hazardous or potentially infectious material, protecting personnel must be the primary concern. However, offering personnel protection does not have to come at the cost of risking product integrity. Class II BSCs provide protection to both personnel and product simultaneously. They maintain an ISO class 5 clean work area for product manipulation, while ensuring that exhaust air is filtered and ducted out of the environment. Thus, a class II BSC is the ideal solution when working with moderately hazardous material and both personnel and product safety are required.
Read more about these lab hoods here regarding their biological safety rating
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Features and Benefits
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Adapting Common Laboratory Hoods for Specialty Purposes
Most hoods designed for specialty applications are derived from standard laboratory configurations (e.g. laminar flow and fume hoods) adapted to specific requirements.
PCR Workstations
Polymerase chain reaction (PCR) is a common technique used in molecular biology to exponentially amplify a target region of DNA or RNA. PCR can turn a single piece of DNA into more than a million pieces in the matter of hours. Unfortunately, a single piece of contaminating DNA can also be amplified, making it extremely important that researchers work within a sterilized area that prevents cross contamination of samples.
PCR workstations were designed to minimize this problem. Adapted from laminar flow hoods, PCR workstations provide HEPA-filtered, sterile air within the hood. These hoods are outfitted with UV-C germicidal lights to disinfect the work surface when the hood is not in use. The lights are also placed on a timer to reduce the risk of UV exposure. In addition to its germicidal properties, UV-C light also causes breaks in strands of DNA that prevent the DNA from being amplified during PCR. Therefore, the UV-C light also serves to prevent carry-over contamination from previous experiments.
Explosion-Proof Hoods
Explosion-proof hoods are a variation of either the laminar flow or exhaust fume hood, designed for work involving potentially flammable material. The conventional motor of the hood is replaced by an NEC Division I-rated non-sparking motor, mounted in a cast-iron, explosion-proof housing. In addition, the hood features an explosion-proof light, and all wiring is encased in filled rigid conduit.
These hoods bear an NEC sub-rating: Division I, Class 1 indicates suitability for use where flammable materials are generally present, and Division I, Class 2 indicates suitability for use when such materials are only intermittently present.
Balance Enclosures
Weighing dry powder chemicals is a routine laboratory task. Weighing procedures frequently result in some of the powder becoming airborne irritants – and potentially toxic threats – to lab personnel. Balance enclosures minimize this danger.
They are essentially ductless fume hoods with a few minor modifications. These negative pressure enclosures direct air from outside the hood through a HEPA filtration system before it is returned to the room. The HEPA filtration system is 99.99% effective in removing particles as small as 0.3 microns in diameter from the air, virtually eliminating the risk of personnel exposure. The front sash of the balance enclosure opens upward, allowing easy transfer of balances into and out of the enclosure.
Nanoparticle Enclosures
These enclosures are essentially balance enclosures that use an ULPA filter, which is 99.995% efficient in removing particles as small as 0.12 microns, to contain the much smaller particles generated during nanomaterial processing.
Explosion-Proof Fan Filter Unit for Hood
UL-listed, NEC Class I, Division 1 Explosion Proof fan/filter unit provides HEPA filtration where solvent vapors, dust and other flammable hazards are present; all conduit and switches also meet explosion-proof requirements.
Explosion Proof 40W LED Light
UL-listed for Class I, Division 1 and 2, Groups C and D areas, this low profile LED light produces 3,600 lumens and operates from 120 to 277VAC, 50/60Hz. The heat-dissipating housing increases the efficiency and lifespan of the LEDs.
Explosion-Proof Power Switches
UL-rated explosion-proof switches are connected to the lights and blowers using specialized conduit with potted fittings. All electrical components are sealed to eliminate potential ignition points.
Explosion-Proof Hoods
Terra Universal WhisperFlow® Hoods and Filter Fan Units- Watch Terra's Vibration Isolation Stand Video
- Vibration Isolation Stand
- Explosion Proof Vertical Laminar Flow Hood
- ISO 5 Explosion Proof Horizontal Laminar Flow Hood
- Explosion-Proof WhisperFlow Hood
- Powder-Coated Explosion-Proof Ductless Fume Hood
Terra Universal WhisperFlow® Hoods and Filter Fan Units This video gives an overview of our WhisperFlow® Laminar Flow Hoods and Filter Fan Units.
This video demonstrates the airflow of our vertical laminar flow hoods. The UL-Listed blower module with cleanroom-grade HEPA filter provides positive pressure laminar airflow to sweep away particulate contamination from the work surface.
This video demonstrates the airflow of our vertical laminar flow hoods. The UL-Listed blower module with cleanroom-grade HEPA filter provides positive pressure laminar airflow to sweep away particulate contamination from the work surface.
Video demonstration of Terra's ISO 5 adjustable vibration isolation stands Watch Terra's Vibration Isolation Stand Video ISO 5 vibration isolation stands adjust to fit a variety of cleanroom equipment
Width and height adjustable stand supports the user on vibration sensitive applications by isolating their equipment from the work surface | 1688-99-30 displayed Vibration Isolation Stand Width and height adjustable stand supports the user on vibration sensitive applications by isolating their equipment from the work surface
Explosion-Proof Vertical Laminar Flow Hoods provide ISO 5-compliant cleanliness in the presence of flammable materials (work surface optional) | 1686-54C-30-SSE displayed Explosion Proof Vertical Laminar Flow Hood Explosion-proof fan/filter unit and light provide ISO 5-compliant cleanliness in NEC Class I, Division 1 locations where solvent vapors, dust and other flammables may be present; order desired work surface separately.
Explosion proof ISO 6 horizontal flow hoods provide a wider critical work zone and eliminate the need for a sash (accessories not included) | 1686-98 displayed ISO 5 Explosion Proof Horizontal Laminar Flow Hood Horizontal-flow explosion proof hoods protect a larger total area of work surface and eliminate the need for a sash.
Terra’s Explosion-Proof WhisperFlow Hoods feature a UL-listed stainless steel fan/filture unit and light | 1686-54C-30-SSE displayed Explosion-Proof WhisperFlow Hood Terra’s Explosion-Proof WhisperFlow Lertical Laminar Flow Hoods features a UL-listed stainless steel HEPA fan/filter unit with light, switch, and other sealed electrical components.
Powder-coated explosion-proof ductless fume hoods shown with optional explosion-proof light (order filters separately) | 2400-18 displayed Powder-Coated Explosion-Proof Ductless Fume Hood NEC Class I, Division 1-compliant explosion-proof fan ventilates fumes through carbon filters for safe indoor release (for use with non-hazardous fumes; order work surface and vapor-sealed or explosion-proof light separately)
Technical Resources
