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Laboratory Fume Hoods and Chemical Containment

All laboratory hoods work on a very basic principle of containment. Negative pressure relative to the exterior is maintained within the interior of the hood to prevent any toxic vapours from escaping and air is drawn at a consistent rate into the hood opening. Experimental procedures are performed within the hood which is consistently and safely ventilated, usually by means of an extract blower and ductwork.

When exhausted to the external environment, chemical fumes are diluted many times over in the atmosphere and become of negligible effect to human health. When environmental concerns are of importance, an extract treatment system, often referred to as a scrubber, can be installed to remove most of the vapours from the exhaust.

Of paramount importance to the safe and effective operation of a fume hood is specify a suitable hood face velocity (the speed at which air is drawn into the opening of the hood). While excessive face velocities can often result in turbulence and reduce containment, insufficient velocities can also compromise hood performance.

In general, a hood inflow velocity of 0.5 m/s or 100 fpm is recommended. Multiply this value by the surface area of the opening of the hood to obtain the air volume required to safely ventilate the hood. As the sash of the hood is lowered, the surface area of the opening decreases. Since the speed of the fan remains unchanged (the case in most hood installations), hood face velocity will increase to maintain extract air volume.

Most hoods are commonly sized for a minimum inflow velocity (eg. 0.5 m/s or 100 fpm) at full sash opening. However, when energy concerns are paramount, an economical way to decrease the amount of tempered air removed from the hood is to size the minimum face velocity of the hood at half-sash opening instead of full-sash opening.

ASHRAE Testing at Esco

Esco Fume Hoods are designed to meet and exceed the latest safety and performance standards of the ANSI/ASHRAE Standard 110-1995. Esco’s in-house ASHRAE testing laboratory at our Research and Development facilities is fully equipped to conduct performance tests on fume hoods according to the ASHRAE Standard requirements.

The ASHRAE 110-1995 Standard is one of the latest and most comprehensive methods for testing the operator safety level of fume hoods, by determining quantitatively and repeatably how well fume hoods contain the gases and vapours released in the work zone. First published in 1985 and extensively revised in 1995, the method employs the following tests to evaluate fume hood performance.

1. Tracer gas containment test: Ensures gas generated inside the work zone is not inhaled by the operator. SF6 (Sul-phur Hexa.uoride) tracer gas is released inside the workzone near the sash window opening (as close as 15 cm behind the sash window) at 4 litres/min. An SF6 detector is mounted on a mannequin to simulate operator breathing (see illustration on the right). A cross draft velocity probe is mounted behind the mannequin during testing to check for cross drafts that may affect the test results.

2. Face velocity measurement: to ensure uniform face velocities at 25%, 50% and 100% sash opening settings. A velocity transducer is connected to a Data Acquisition System, which calculates the average of 300 velocity readings at each measurement location.

3. Local smoke visualization: tests along workzone joints and corners

4. Gross smoke visualization: tests overall cabinet air.ow pattern. The above two smoke visualization tests ensure smooth and direct air.ow inside the workzone towards the air.ow outlet passages.

Main Features

Laboratory fume hoods are one of the most important components used to protect laboratory personnel from exposure to hazardous chemicals and agents used in the laboratory. They can provide an effective backup safety device for the containment and exhaust of toxic, offensive, or . ammable materials when the containment of an experiment or procedure fails and vapours or dusts escape from the apparatus being used.

Industrial-grade support structure constructed of electro-galvanised steel and aluminium with a corrosion and abrasion resistant oven-baked powder-coated . nish.Internal liner is constructed of phenolic resin laminates; more corrosion-resistant and durable than other common internal liner materials (refer to page 7 of this catalogue for the chemical resistance report / test results for the phenolic resin laminate material).

Single wall design ensures the internal workzone width is maximized.

Instant-start electronically ballasted 5000k lighting system is . icker-free and the warm glow of the lighting system is comfortable to the operator’s eyes during extended hours of usage. Integral . uorescent lighting is isolated from the air stream in order to increase air. ow uniformity.

Standard vertical rising fail-safe counterbalanced sash. The sash will tilt and lock if a cable snaps; Optionally, horizontal sliding sashes or combination horizontal / vertical sashes are available; all sashes are constructed of tempered glass for maximum operator safety.

State of the art baf. e system constructed of phenolic resin laminates delivers maximum containment by ensuring air. ow uniformity throughout the main chamber of hood.

Aerodynamic design eliminates air turbulence within the hood which can otherwise compromise containment; noise levels and static pressure losses are also minimized. Aerodynamic curved side pro. le improves containment.

Corrosion-resistant stainless steel airfoil provides spill retention and safely ventilates fumes generated towards the front of the hood for superior operator protection; the curved front edge also facilitates an ergonomic working position.Generously-sized work room due to improved positioning of the service . xtures.Black colour work surface resists staining. Work surface is included with optional base cabinet.No exposed metal screws are present in the work zone construction, which improves corrosion resistance of the body. Electrical system is designed to meet the latest international regulations and standards for safety.

Designed to meet and exceed the latest safety and performance requirements of the ANSI/ASHRAE Standard 110-1995;when ordered with a modified control system, these units will also comply with the British / Australian / New Zealand standards BS 7258, AS 2243.8 and NZS 7203.Standard systems are shipped fully-assembled; however, units can also be shipped unassembled to lower freight handling costs; our industry-exclusive aluminium extrusion modular system makes re-assembly quick and eficient.

Technical Specifications :

General Speci.cations EFH-4AX EFH-5AX EFH-6AX
External Dimensions (L x D x H) 1200 x 875 x 1500 mm
47.2" x 34.4" x 59.1" 1500 x 875 x 1500 mm
59.0" x 34.4" x 59.1" 1800 x 875 x 1500 mm
70.9" x 34.4" x 59.1"
Internal Workzone Dimensions (L x D x H) 1120 x 680 x 1200 mm
44.1" x 26.8" x 47.2" 1420 x 680 x 1200 mm
55.9" x 26.8" x 47.2" 1720 x 680 x 1200 mm
67.7" x 26.8" x 47.2"
Maximum Sash Opening 580 mm / 22.8" (standard vertical rising sash)
Recommended Maximum Exhaust Air Volume
For minimum face velocity of 0.5 m/s or
100 fpm at full-open hood sash position Required Fume Hood
Exhaust Air Volume
1170 cmh / 690 cfm Required Fume Hood
Exhaust Air Volume
1480 cmh / 870 cfm Required Fume Hood
Exhaust Air Volume
1795 cmh / 1055 cfm
Recommended Minimum Exhaust Air Volume
For minimum face velocity of 0.5 m/s or
100 fpm at half-open hood sash position Required Fume Hood
Exhaust Air Volume
585 cmh / 344 cfm Required Fume Hood
Exhaust Air Volume
740 cmh / 436 cfm Required Fume Hood
Exhaust Air Volume
900 cmh / 530 cfm
Inner Exhaust Outlet Diameter 252 mm / 10.0" 252 mm / 10.0" 305 mm / 12.0"
Outer Exhaust Outlet Diameter 266 mm / 10.5" 266 mm / 10.5" 319 mm / 12.6"
Light Intensity at Work Surface 780 Lux / 72 foot candes
Construction
Main body: Phenolic resin laminates

Support frame: Aluminium extrusions with an oven-baked epoxy powder-coated .nish
Interior baf.e system: Phenolic resin laminates
Airfoil: Stainless steel grade 304
Power Consumption 60W (Fluorescent Lighting & Microprocessor Control System)
Net Weight 140 kg / 310 lbs 170 kg / 370 lbs 210 kg / 460 lbs
Crating Size (unassembled hood) 1550 x 1100 x 500 mm

61.0" x 43.3" x 19.7" 1700 X 1100 X 500 mm

66.9" x 43.3" x 19.7" 1850 X 1100 X 500 mm

72.8" x 43.3" x