FUME HOODS

Requirement for Fume Hoods

• handling of hazardous materials (solids, liquids or gas)
• prevents exposure to fumes, vapours, dusts, and aerosols carried in air
• provides a cleanable work surface
• a temporary work surface - not a storage unit
• breathing zone - the volume of air around your nose and mouth which has the potential to be inhaled under normal circumstances
• face velocity - inward airflow from the sash in feet per minute (fpm)
• safe working sash height is variable

Fume Hood Anatomy

• sash
• by-pass grill (CAV)
• work surface
• air foil
• baffles
• access ports
• controller module
• light switch
• utility supplies
• electrical supply
• storage units

Alarms or Monitors

• never turn off or deactivate alarms or monitors
• if the alarm sounds or the monitor lights indicate low flow:
  • work should be stopped, close all containers, equipment turned off, and the sash lowered
  • lab personnel should leave the area if highly toxic or volatile chemicals are being used
  • if there is a likelihood that airborne contaminants will be released from the fume hood into the laboratory, please immediately contact your building services
  • report all problems to your supervisor immediately
• verify control panel on your unit
• read user manual
• monitor air flow alarm
• MUMC fumehoods using VentAlert system can change their battery according to these instructions.

Environmental Protection

• fume hoods exhaust 100% of the air into the environment
• no protection of the environment from hazardous fumes, vapors, aerosols and dusts
• minimize these hazardous releases by keeping containers closed at all times
• evaporation is prohibited as a method of chemical waste disposal

Sustainability

• conditioned air (heated or cooled, humidified or dehumidified) is exhausted through fume hoods
• fume hood exhaust systems run 24 hours a day, 7 days a week
  • are not put in low consumption states during off hours in the building like the air handling units
• constant air volume systems are present in some buildings
  • do not allow for 'emergency purge' of fume hood even if you do have a controller panel with an emergency purge button
  • air consumption is not altered when the sash is closed
    • airflow increased through by-pass and air foil
• variable air volume systems are present
  • allows for emergency purge of fume hood via controller panel if that feature is present
  • air consumption decreases when sash is closed

Specifications for Fume Hoods

• manufacturer's specifications
• user manual
• CSA Z316.5-15, "Fume hoods and associated exhaust systems"
• SEFA 1-2010, "Recommended Practices For Laboratory Fume Hoods"
• ASHRAE 110-2016, “Method of Testing Performance of Laboratory Fume Hoods"
• AEBC R-52 rev 1, "Design Guide for Basic and Intermediate Level Radioisotope Laboratories".

Preparing a Fume Hood for Work

• review the SDS for the chemicals in use, review SOPs for work to be done
• don PPE (lab coat, chemical resistant gloves, long pants, close toed shoes, eye protection)
• verify an appropriate chemical spill kit is available
• ensure you are aware of the closest emergency eyewash and shower
• turn on the light, test the alarm and verify inflow velocity on the controller panel
• verify certification is up to date by viewing sticker
• open the sash and load your equipment, samples and reagents
• work at least 6" inward from the air foil
• do not block rear baffles
• raise large objects by 3"
• lower sash to working height or close vertical panels to ensure one panel is in front of you

Working in the Fume Hood

• monitor the fume hood when performing ongoing or reactive experiments
• keep pedestrian traffic to a minimum
• avoid rapid or excessive movement in front of the fume hood
• place:
  • experimental materials and equipment at least 6 inches back from the face
  • large objects two to three inches above the work surface
• keep rear baffle openings clear
• keep papers, paper towels, work surface diapers, vials, and other small objects from being drawn into the fume hood’s ventilation system

Maintain Air Flow

• be aware of eddy currents inside the hood
• never cause air turbulence close to the fume hood eg exhaust from other equipment
• keep nearby doors and windows closed when working in a fume hood
• keep people traffic away from a fume hood when in use
• move slowly in the hood
• don’t open the sash rapidly

Small Chemical Spill in Fume Hood

• stop working immediately and assess for
  • personal contamination (proceed to emergency flushing equipment)
  • hazardous material release from fume hood
  • potential for fire or explosion
  • equipment damage
  • air flow status
• notify laboratory occupants
• retrieve chemical spill kit
• apply absorbent materials
• apply chemical neutralizer
• collect absorbed liquids into a double poly lined bag, labelled
• complete incident reporting per RMM1000

Heat Generation

• equipment and experimental procedures can generate excessive heat
• heat causes changes in air currents
• heat causes air to expand
• negative pressure of the fume hood may be overcome leading to relase into the user's breathing zone

Over Crowded Fume Hood

• over-crowded fume hoods are a hazard
• dispose or donate excess chemicals
• move chemicals do another flammables / corrosives storage unit
• prop up large equipment on blocks to allow air flow
• most vapours flow down and accumulate at the work surface
• recommend use of fume hood shelves

Other Precautions

• do not use hot plates or heated stirrers in a fume hood  when flammables or combustibles are present
• never use paper, paper towel, kimwipes or any light items which can get sucked up into the ducting
• evaporation of hazardous chemicals is prohibited as a method of disposal
• never modify a chemical fume hood
• no other types of exhaust can be connected to the fume hood exhaust system without a proper engineering assessment by Facilities Services or your hospital host engineering department

Perchloric Acid Fume Hood

• use of perchloric acid requires a specialized fume hood
• contact fhsso@mcmaster.ca if you have or use perchloric acid
• stainless steel liner
• coved corners
• washdown system for ducting
• removable baffles

Radioisotope Use

• radioisotope use requires a fume hood designed for this purpose
• approval from health physics
• fume hood is assigned to you

After using Fume Hood

• secure all containers of hazardous materials
• let the fume hood run for 5 minutes
• remove all hazardous materials and equipment
• clean all work surfaces with water
• fully close the fume hood sash

FHS Equipment Inventory Labels

• all fume hoods in MUMC should have a FHSSO inventory label affixed. If there is no label, please notify fhsso@mcmaster.ca
• site visit to evaluate fume hood and affix label
• send fhsso@mcmaster.ca notification emails
  • when unit has been removed
  • when unit requires to be put out of service
  • when unit has been inspected or certified
  • when unit's contact person is updated
  • when there is an issue with the unit

Maintenance and Annual Certification

• fume hoods are to be maintained by the users according to the manufacturer's instructions regardless of location
• malfunctioning fume hoods are to be reported and put out of service
  • applying signage
  • notifying lab occupants
• on campus buildings (MDCL, IAHS and CRL) are serviced by Facility Services
• off-site locations are responsible for servicing their own fume hoods through the building's engineering department or external service provider
• in all cases the fume hood is to be free of hazardous materials prior to servicing

Cleaning the Fume Hood

• use cleaning solutions compatible with the chemicals in use
• use cleaning solutions compatible with the surfaces of the fume hood
• follow manufacturer's instructions for cleaning fume hood
• clean the interior and exterior surfaces and sash periodically and after spills using deionized water; then wipe the areas down with a soap solution and rinse
• use a long handled tool to reach back and sides of the fume hood
• use a purpose tool for the sash i.e. the Glass Slider or the Glider
  • https://www.youtube.com/watch?v=YzA7YFX3HQo
  • https://www.youtube.com/watch?v=ey0j0G9wNP0

Emergency Exhaust

• your fume hood may have a controller and an option for emergency exhaust
• depending on your the HVAC system design, you may have constant air volume or variable air volume exhaust
• constant air volume systems do not have the ability to increase exhaust even if your fume hood has a control panel with an emergency exhaust button
• contact your building maintenance service to verify if your emergency exhaust switch on your fume hood is active

Downdraft Tables

• downdraft or necropsy tables are specially designed work areas with ventilation slots on the sides of the work area
• useful for work with human anatomical specimens and animal perfusions and other uses of chemicals with vapor densities heavier than air
• stainless steel table on wheels with slotted sides to capture toxic vapours and fumes from anatomical specimens
• also contains a sloped surface designed to collect fluids in a collection container beneath the table
• port for attaching exhaust source, detachable for movement of cadavers
• detailed equipment-specific training through the anatomy program

Elephant Trunks or Snorkels

• local exhaust ventilation
• not a substitute for a fume hood
• potential for contaminants to enter the user's breathing zone is high
• requirement for LEV to be registered with FHSSO and reviewed by JHSC
• SOPs to be generated by users and reviewed by JHSC
• tubing attached to the ventilation system to allow for highly localized exhaust
• exhaust area is very limited
• must be very close to hazard for effectiveness
• capture of contaminant is only effective within a distance of one duct diameter
• capture velocity required is dependent on the application i.e. passive capture or active capture
• flanged openings capture more contaminant than non-flanged openings

Fume Canopy

• constructed in a similar fashion to the overhead canopy hoods seen in kitchens
• in order for the canopy hood to be able to capture contaminants, the hood requires a relatively large volume of air movement, making them somewhat costly to operate
• the canopy hood works best when the thermal or buoyant forces exist to move the contaminant up to the hood capture zone
• they are designed such that the contaminated air passes through the user's breathing zone
• the airflow is easily disrupted by cross currents of air
• canopy hoods should only be used for exhaust of non-hazardous substances i.e. steam, odors from urine or fecal samples
• capture velocity required for effectiveness highly dependent on contaminant and process employed
• ACGIH Ventilation Manual

Other Ventilation Equipment

• slot ventilation table
• walk-in fume hoods
• glove boxes

Follow Up Expectations

• this awareness information to explain principles of equipment and basic function
• supervisor or competent person to demonstrate functioning of a fume hood, any special features and emergency procedures
• your supervisor shall ensure that you are to be chaperoned until the supervisor or competent person deems that you are proficient in fume hood use
• your supervisor shall provide you with equipment-specific, experiment-specific and lab-specific SOPs related to the fume hood
• if you are unsure about anything, ask your supervisor or contact the FHS Safety Office fhsso@mcmaster.ca

 

Updated 2021-11-09