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Fume Hood Standard

Selection Criteria

An assessment should be made of the anticipated processes before a fume hood is selected to ensure that users are adequately protected and the fume hood may be expected to perform reliably.
These include the following:

  1. chemical attack;
  2. chemical toxicity;
  3. radioactive contamination;
  4. solvent attack;
  5. thermal stress;
  6. adsorption and absorption of hazardous substances;
  7. explosions;
  8. fire;
  9. mechanical stress, e.g., vibration; and workplace environment.

Manufacturers Information

The following information should be obtained from the manufacturer:

The fume hood must meet the minimum design criteria outlined in CSA Z316.5-94. and meet or exceed performance standards  specified by ANSI/ASHRAE 110-1995 .


Used Fume Hoods

Use fume hoods must be approved by UW design section in conjunction with the Safety Office.  Persons wishing to purchase previously used fume hoods are responsible for obtaining the following:


Decontamination Certificates from previous owners for:

  1. Radioactive contamination
  2. Biological contamination
  3. Chemical contamination


Information from the manufacturer:

  1. type of fume hood and exhaust system;
  2. identification of all materials of construction;
  3. dimensioned drawings of the fume hood;
  4. results of the evaluation in a test facility;
  5. operating and maintenance instructions for all the equipment; and
  6. any specific limitations on use.

Construction

Materials

All materials, including service fittings and exhaust systems, shall be resistant to the chemicals and substances specified as permissible for use within the fume hood.

  1. tempered plate -glass shall be used.
  2. plastic is used, it shall be a fire-retardant grade.
  3. coatings and finishes shall be fire resistant.
  4. sealants and adhesives shall exhibit good chemical and thermal resistance and suitable mechanical properties.

Cabinet

  1. work surface shall have raised edges (1/2") and sealed to help contain any spills.
  2. work surface shall be strong enough to bear the weight of any necessary apparatus.
  3. sash openings shall incorporate airfoils to inhibit refluxing of air at the face opening.
  4. the rear and top of the hood shall be supplied with 3 baffles, the top and bottom being adjustable.

Electrical

  1. Fume hoods and exhaust systems shall comply with the applicable requirements in CSA Standards C22.1 and C22.2 No. 151 or C22.2 No. 1010.1.

    Note: The risk assessment may identify the fume hood and immediate surroundings as hazardous locations requiring special (e.g. explosion-proof) electrical equipment. The criteria for determining the degree of hazard and the appropriate type of electrical equipment are provided in Section 18 of the Canadian Electrical Code, Part 1. In order to obtain proper electrical classification of hazardous locations, ft is necessary to contact the local authority having this jurisdiction.

  2. All electrical receptacles shall be readily accessible and external to the fume hood interior.
  3. A ground fault interrupter should be used in the electrical power supply where necessary.

Services

  1. All plumbing and electrical services shall be installed such that they can be readily connected or disconnected, either by design of the assembly or via an access panel in the fume hood interior or exterior.
  2. All valves shall be accessible for maintenance.
  3. All service fixture controls (e.g. gas, air, water, vacuum) shall be external to the fume hood, clearly identified and within reach.
  4. All service fixtures within the workspace shall be corrosion resistant or have a corrosion resistant finish.
  5. If water service is provided, the fume hood shall have provisions for a suitably designed drain.
  6. Light fixture(s) mounted exterior to the fume hood liner shall be protected from the fume hood interior by a sealed, transparent, impact-resistant vapour shield.
  7. Light fixture(s) mounted inside the fume hood liner shall be protected against corrosion.
  8. Light fixture(s) mounted inside the fume hood liner shall be vapour proof.
  9. Light fixture(s) shall be capable of providing an il luminance at the work surface consistent with the level required by Part VI of the Canada Occupational Safety and Health Regulations.

Alarms

  1. A fume hood shall have an audible and visual alarm to indicate to the user when the air flow deviates from the set point.
  2. The alarm shall be readily visible to the user during use of the fume hood.
  3. Only authorized personnel shall be able to adjust the alarm set point.
  4. The alarm shall remain functional in the event of loss of mains electrical power.
  5. Battery power supplies shall have a low charge indicator.

Exhaust System

General

Exhaust duct, fan, and scrubber materials should be chosen based on compatibility with the materials handled in the fume hood, as well as compatibility with the installation and maintenance of the fume hood.

Exhaust Ducts

  1. Exhaust ducts should be constructed to SMACNA Seal Class B Standards as a minimum.
  2. Exhaust ducts should be maintained under negative pressure.

    3. Note: This will reduce the possibility of contaminants leaking into the building. Even with a remotely located. exhaust fan, the discharge side of the exhaust fan provides a positive pressure.

  3. Fume hoods with integral fans shall have appropriately constructed exhaust ducts.
  4. Each fume hood should be separately ducted to a point outside the building. Perchloric acid fume hoods shall be separately ducted to a point outside the building. Radioisotope fume hoods shall be separately ducted to a point outside the building, unless located in the same room.
  5. The exhaust stack shall be located so as to ensure acceptable dilution and dispersion of exhaust air and to preclude exhaust re-entry through air intakes and building openings.
  6. The exhaust stack shall not be fitted with devices, which deflect the effluent or reduce the discharge velocity.

    7. Note: Rain protection by weather caps and swan neck ducts are examples of such devices.

  7. Thermoplastic materials shall not be used for duct work.
  8. Fire-retardant material or carbon steel with an acid-resistant coating may be used for general chemical applications.
  9. Stainless steel ducts shall be used for perchloric acid fume hoods.
  10. Corrosion-resistant ducts shall be used for radioisotope fume hoods.
  11. Vitrified clay pipes with sealed joints may be used for acidic, alkaline, and plating solutions

Exhaust Fan

  1. Exhaust fans should be positioned as close as possible to the termination (discharge end) of the duct, preferably on the roof.

    2. Notes:From the fan position to the termination of the duct, the internal pressure is positive and any leaks in the duct will allow the escape of contaminants from the duct into the surrounding spaces.
    Consideration should be given to protecting the fan from the effects of adverse weather conditions.

  2. The fan motor should be mounted outside the exhaust duct for easy access and to avoid contamination of the motor. Appropriate shaft seals shall be employed.
  3. Glass fibre, PVC, or equivalent fans shall be used for highly corrosive conditions.
  4. Coated steel, glass fibre, or PVC fans may be used for low to moderately corrosive conditions.
  5. Fans shall be sized to provide adequate exhaust air flow. The static pressure losses of the fume hood and associated duct work shall be included in the determination of fan size.

Types of Fume Hood

Special Design Criteria for Perchloric Acid Fume Hoods

Perchloric acid fume hoods shall comply with the criteria described in this standard and with
The following additional requirements:

  1. Fume hoods designed for and used with perchloric acid shall be identified by a prominent and permanent label indicating suitability for use with perchloric acid procedures.
  2. All exposed parts of the fume hood interior shall be suitable for use with perchloric acid.
  3. The work surface shall be watertight and furnished with a raised lip to contain spills and wash down water.
  4. The fume hood shall be provided with a water spray (wash down) system for rinsing the duct work from point of discharge to the fume hood collar and also the area behind the baffle.
  5. The duct work shall be self-draining with no horizontal sections.
  6. Service fitting controls for internal outlets and for the wash down systems shall be external to the fume hood, clearly identified, and within easy reach.
  7. The baffle shall be removable to allow periodic inspection for damage/corrosion.
  8. The fume hood shall be constructed of nonporous, inorganic, acid-resistant, non reactive material, and shall be impervious to perchloric acid.
  9. Specially designed fans shall be used.

Installation

Location

Fume hoods shall be installed according to the manufacturer's instructions.

  1. Fume hoods should be located out of the normal, traffic pattern and away from interfering room air currents.
  2. Seated work stations shall not be located directly opposite fume hood openings.
  3. The distance between the side of the fume hood and a wall or large architectural obstruction (e.g., an architectural column) protecting beyond the plane of the sash should be at least 0.3 m

    4. Note: The adjoining wall may present a partial obstruction which may affect intake air flow.

  4. The user's unobstructed personal work area should extend at least 1.5 m from the face of the fume hood.
  5. The distance between the sash and an opposing wall or other obstruction likely to affect the air flow should be at least 2.0 m.
  6. Fume hoods should not be installed face to face nor opposite a biological safety cabinet unless the distance between them is at least 3.0 m .
  7. The distance between the sash of the fume hood and a doorway should be at least 1.5 m.
  8. The distance between the side of the fume hood and a doorway should be at least 1.0 m
  9. Any room air supply diffuser should not be within 1.5 m of the sash and shall not affect fume hood performance.

Exhaust Duct Installation

  1. The exhaust duct should be self-draining and proceed to the discharge point with as few horizontal sections as possible.

    Note: This is to minimize areas in which condensates or liquids coming in from the discharge point can collect.

  2. Ducts shall be sealed, according to SMACNA Seal Class B Standards, to prevent leakage
  3. The following information shall be recorded when the fume hood and exhaust system is installed:

    • "as built" drawings showing the complete installation;
    • identification of the materials of construction;
    • operating and maintenance instructions; and
    • make, model, and serial number.

Commissioning

After installation UW Plant Operations Design Section shall notify Plant Operations Maintenance Section to commission the fume hood.
Commissioning shall include, but not be limited to, determinations of the following:

  1. electrical safety;
  2. adequate lighting;
  3. noise level;(less than 55 dBA)
  4. the functioning of components and services; and
  5. field performance test results as specified in Clause 11.4 CSA Z316.5-94.

Field Test

  1. All test and measurement equipment shall be accurate and properly calibrated as specified in CSA Standard CAN/CSA-Q419.
  2. The building ventilation system shall be operating correctly, the room doors and windows in their normal position, and all other fume hoods and exhaust systems operating at design conditions.
  3. Fume hoods shall normally be tested empty. However, in exceptional circumstances, it may be essential for the safety of the verifier to test a fume hood with fixed equipment in place.
  4. Face velocity shall be measured and the test results shall be compared with the values provided by the manufacturer. The test results shall be documented and provided to the user.
  5. The sash is open to a normal working height.(approximately 18")
  6. The minimum face velocity is between 100 to 120 fpm.
  7. The maximum sash working height is marked

Sash Operation

  1. Sash operation shall be smooth and easy throughout its travel.
  2. Sash(es) shall be operable from either end with one hand.
  3. Sash counterbalances should operate without interference or restriction.
  4. Vertical rising sashes shall hold at any set height without creeping up or down.
  5. All adjustable baffles shall operate freely,'without binding or restriction.
  6. The alarm shall function properly and indicate unsafe conditions when the air flow is restricted.

Maintenance

General

Before an inspection or any maintenance work is performed, the extent of hazards resulting from contaminated surfaces shall be assessed and any necessary personal protective equipment or clothing shall be used. The laboratory supervisor is responsible for removal of any material located in the fume hood.

Wash down systems should-be regularly used and properly maintained.
Note: This is to facilitate the removal of corrosive condensates from the interior surface before damage occurs.

Twelve Month Maintenance

Every twelve months, the following maintenance operations will be performed By UW Plant Operations Maintenance Sections:

  1. inspect the fans, motors, drives, and bearings for correct operation;
  2. test the controls of the services to the fume hood for proper operation;
  3. inspect the fire damper and the release mechanism;
  4. measure the fume hood face velocity and compare to fume hood specifications, correct as necessary;
  5. test the operation of the air flow alarm; and
  6. repair defects and lubricate as necessary.