Laboratory Apparatus

Laboratory work requires a wide variety of apparatus and equipment. This page describes basic safety principles. Before using any piece of equipment, specific training on operating that equipment is required. Users must also be familiar with safe operating procedures and be able to demonstrate these to the supervisor. Select a topic below for more information.

General equipment safety requirements

Equipment and apparatus

Machine guarding

Devices, equipment, and apparatus that have exposed moving parts require guards to limit contact with these parts. In most cases an evaluation must be made to address the level of hazard and need for guarding. 

Most laboratory equipment is purchased with appropriate guards, however, it is the supervisor’s responsibility to ensure that the guarding in place is protective of workers operating the equipment. Once guards have been put in place, they are not to be moved or altered by any person other than those trained and authorized to perform work on the machines without guards. Maintenance procedures must be carried out by individuals who are trained to perform maintenance safely.

Industrial regulations references to machine guarding

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Autoclaves

Autoclaves are pressurized sterilizing chambers generally used to sterilize glassware, instruments, gloves, liquids in bottles, biological waste, and other materials by steam under pressure.

Autoclaves are typically at pressures a little under two atmospheres and temperatures of up to 135°C. When working with autoclaves, workers need to be aware of potential hazards such as explosions. The stored energy in the steam is tremendous and autoclaves differ from other steam receivers in that they have to be opened frequently, and residual pressure may not be detectable by the pressure gauge.

Legislation

Boilers and Pressure Vessels (O. Reg. 220/01) part of TECHNICAL STANDARDS AND SAFETY ACT, 2000. This regulation applies to autoclaves with over a 1.5 cubic ft. capacity (42.5 L) or working pressure of 15 psi (103 kPa) and greater.

Operations
  • Written operating procedures are essential. These should be located in the lab and available to all users.
  • Every operator should be adequately trained in the operation of an autoclave. In particular, they should be made aware of and understand the importance of:
    • Wearing appropriate personal protective equipment at all times
    • Proper packaging, loading and unloading practices
    • Ensuring that the autoclave is completely vented before attempting to open the door
    • The function of all operating controls and door interlocking devices
    • The danger of interfering with or bypassing any safety device
    • The correct application of the locking stirrups, swing bolts or door locking mechanism
  • An operator who has not yet acquired sufficient knowledge and experience must be kept under proper supervision by a competent person.

Quality control

Quality control measures must comply with the manufacturer’s recommendations and well documented.

  • Mechanical: time and temperature graphs, charts or printouts, done during each cycle
  • Chemical: time/temperature and/or humidity sensitive tape, strips or pellets, done on each cycle
  • Biological: spore-laden strips or vials, done weekly or more frequently if recommended by manufacturer

Controls
  • A suitable reducing valve or other automatic appliance to prevent the safe working pressure from being exceeded.
  • A suitable safety valve adjusted to permit steam to escape as soon as the safe working pressure is exceeded.
  • An accurate steam pressure gauge to indicate the pressure of the steam in the vessel.
  • One isolating valve for each autoclave.
  • Interlocks between the door locking mechanism and the steam inlet valve to ensure that steam cannot be turned on unless the door is properly closed and fully locked. The door cannot be unlocked unless the steam inlet valve is closed and the exhaust valve is completely open.
  • A test cock or other equivalent device to give an audible and visual indication of internal pressure in the autoclave. This test cock has to be interlocked with the door locking mechanism so that the test cock will be completely open before the door can start to unlock.

General safety

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Centrifuges

Centrifuges are laboratory instruments that have the potential to cause serious injury and considerable damage if safe operating and maintenance procedures are not followed. All lab workers operating centrifuges must be adequately trained in safe centrifuge operation.

The principal investigator is responsible for ensuring that workers are trained, that rotor use logs are maintained, and that rotors are retired when required.

General centrifuge safety procedures
  • All users must read and be familiar with the user's manual of the particular model they will be using. The user's manual should be kept in a location easily accessible to the centrifuge and it's operators.
  • Do not operate a centrifuge without training on the specific make and model. Prior to operation, check that the classification decal on the ultracentrifuge matches the decal on the rotor. Check that the correct over speed disk is located on the bottom of the rotor.
  • Rotor logs must be kept for every ultracentrifuge and include the user name, date, duration, number of revolutions, speed of use, and notes on the condition of the rotor at time of use.
  • Rotors must be retired after the number of revolutions or years of service stated by the manufacturer, unless an annual stress test permits continued use. The rotor manufacture date will be included on the rotor log.
  • Ultracentrifuges must be operated on a stable, resonance-free surface with at least 15 cm clearance at sides and 10 cm clearance at rear. Movement of the apparatus can damage the unit or cause injury.
  • Units should be located away from flammable chemicals or combustible liquids.
  • Centrifuges must not be left unattended until full operating speed is attained and operation has been monitored for vibration.
    • If vibration occurs, the centrifuge must be stopped immediately and load balances checked.
  • Use only the specific rotors for a centrifuge. Never substitute alternate models.
  • Never exceed the manufacturer's maximum speed and sample density ratings for each rotor. Take extra care to adhere to speed reduction recommendations for high-density solutions, plastic adapters or stainless steel tubes.
  • Always balance sample loads and ensure that swinging bucket rotors are completely filled. Do not leave empty buckets.
  • When using samples that are hazardous chemical, biohazardous, or radioactive, rotors must have aerosol containment (O-rings). Biohazard work may also be done in a biosafety cabinet and samples should always be loaded/unloaded in the cabinet. In general, samples should be capped to prevent aerosol formation.
  • Never open a centrifuge while it is running. Prior to operation, check that interlocks function to prevent opening while in operation.
  • Do not reuse plastic ultracentrifuge tubes.
  • Rotors and cups must be cleaned after each use with a non-corrosive cleaning solution, rinsed well and stored inverted. Do not use plastic bristle tube brushes to clean cavities.
  • Store fixed angle vertical tube and near-vertical tube rotors upside down, with lids or plugs removed. Swinging bucket rotors should be stored with caps removed.

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Fume hoods

Fume hoods reduce levels of hazardous products produced or used during experiments by confining them to an area separate from the laboratory, diluting them with large quantities of air, and expelling them long distances from the building.

There are several different types of fume hoods at the University of Waterloo. Among these are:

In addition, there are special fume hoods for perchloric acid and radioisotopes. Therefore, one must ensure that the appropriate hood is used for each specific reaction or process involving specific chemicals. This information must be provided to students by the laboratory supervisor or laboratory assistants.

Typical bypass fume hoods

A typical modern fume hood consists of the following components:

Airfoil: Located at the bottom and sides of the fume hood entrance the airfoil reduces turbulence in the air entering the hood near the edges.

Air baffle and adjustable slots: Air baffle and adjustable slots are used to insure a laminar flow through the hood and to decrease turbulence.

Sliding sash: Allows full access to the fume hood when setting up an experiment and partial or full closing while running the experiment to insure proper evacuation of hazardous products.

Bypass slots: Bypass slots are sequentially uncovered as the sliding sash is closed, allowing more air to enter through the bypass slots and less through the sash opening. This keeps the face velocity relatively constant. If there are no bypass slots the velocity through the fume hood opening would increase as the sash is closed to a point where turbulence would force hazardous materials out of the fume hood ant into the laboratory. Flow rates could also increase to the point at which experiments are physically disrupted by the air flow.

Exhaust duct and damper: The exhaust duct damper is used to set the face velocity of the fume hood. This is normally set between 80 and 120 FPM with the sash set at normal working height. All fume hoods are to be ducted as per regulation 308 in the Environmental Protection Act.

Construction: Material used in construction should be non-porous and impervious to materials used or produced. For example stainless steel is very good for most radioactive material because it is easily cleaned but will break down when halogenated acids such as hydrogen chloride are used.

Walk-in fume hood

Walk-in fume hoods are basically a ventilated room with an air baffle at the back and adjustable slots to insure laminar flow. Access is normally gained by sliding or folding doors. These fume hoods are mainly used to set up large-scale experiments or processes. Experiments are erected in the walk-in fume hood, the doors are closed, and the experiment is monitored or controlled remotely. No protection is provided to persons while inside the walk-in fume hood.

Self-contained fume hoods (ductless)

Self-contained fume hoods are designed similar to conventional by-pass fume hoods but are not ducted to the outside. The air is instead passed through activated charcoal for organic compounds or through a HEPA filter for particulate material and the clean air is returned to the laboratory.

Filters
  • The filters must be appropriate to the type of material used or produced and replaced prior to failure.
  • Life times of HEPA filters are simple to monitor using pressure changes and an external gauge will indicate when it is time to change the filter. These types of hoods are used to handle dry materials as well as in some bio-hazards.
  • Life times and absorption efficiencies of activated charcoal filters are extremely variable and should only be used with very low hazard chemicals. All ductless fume hood installations must be approved by the Safety Office.
  • Ductless fume hoods must not be used for flammable solvents as per Section 4.12.8.3 of the Ontario Fire Code.

Perchloric acid fume hoods

Perchloric acid fume hoods are to be installed and used whenever processes involve the production of perchloric acid fumes. This type of hood is designed to prevent the deposition and build up of perchloric salts on the hood or duct surfaces. Perchloric acid hoods are designed with wash down devices that periodically (after each use) rinse the fans ducts and fume hoods surfaces with water. The fume hood and duct work is made of stainless steel and the duct work is kept straight, vertical and as seamless as possible to aid in washing away perchloric salts.

  • Heating perchloric acid should be undertaken with extreme caution.
  • Do not use oil baths or open flames to heat perchloric acid.
  • Do not dry filter paper used to collect perchloric acid precipitates.
  • Keep perchloric acid away from organic chemicals especially alcohols and glycerol.
  • Store perchloric acid in ceramic trays.

General fume hood information

Fume hood safety
  • Make sure that the exhaust blower is operating and air is entering the hood, prior to starting an experiment. All fume hoods at UW are fitted with a Vent Alert flow monitor. If the monitor is alarming or not functioning please call Plant Operations 24 Hr. service number ext. 33793. If the hood is not working properly please call Plant Operations 24 Hr. Service number ext. 33793and have the hood repaired prior to using it.
  • Do not place your face inside the hood. Keep hands out as much as possible. Perform all work involving hazardous or volatile materials in operating fume hoods.
  • Connect all electrical devices outside of the hood to avoid sparks which may ignite a flammable or explosive chemical.
  • Note that the hood is not a substitute for personal protective equipment.
  • Always work at least 6 inches in from the opening of the fume hood.
  • Do not modify fume hood.
  • Do not use your fume hood as a storage area
  • Avoid blocking off baffle exhaust slots in any manner. Elevate large equipment "2" inches off the base of the fume hood.
  • Large pieces of equipment or numerous persons standing in front of the fume hood will cause turbulence.
  • Be aware of other room ventilation factors that may interfere with your fume hood operation, such as open doors to labs, open windows, blocked exhaust ports or heating and air conditioning vents.
  • Avoid cross drafts and disruptive air currents in front of the fume hood.
  • Use the sash as a safety shield when boiling materials or conducting an experiment with reactive chemicals.
  • Prepare a plan of action in case of an emergency, such as a power failure, especially when using extremely hazardous chemicals or acids.
  • Work with the sash at the proper operating level as indicated by the arrows.
  • When fume hood is not in use, keep sash closed.
  • When fume hood is not in use, ensure that all materials are in sealed containers.

Fume hood standards

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:

  • Chemical attack
  • Chemical toxicity;
  • Radioactive contamination;
  • Solvent attack;
  • Thermal stress;
  • Adsorption and absorption of hazardous substances;
  • Explosions;
  • Fire;
  • Mechanical stress

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:

  • Radioactive contamination
  • Biological contamination
  • Chemical contamination 

Information from the manufacturer:

  • Type of fume hood and exhaust system
  • Identification of all materials of construction
  • Dimensioned drawings of the fume hood
  • Results of the evaluation in a test facility
  • Operating and maintenance instructions for all the equipment
  • 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.

  • Tempered plate glass shall be used.
  • If plastic is used, it shall be a fire-retardant grade.
  • Coatings and finishes shall be fire resistant.
  • Sealants and adhesives shall exhibit good chemical and thermal resistance and suitable mechanical properties.

Cabinet

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

Electrical

  • 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, it is necessary to contact the local authority having this jurisdiction.
  • All electrical receptacles shall be readily accessible and external to the fume hood interior.
  • A ground fault interrupter should be used in the electrical power supply where necessary.

Services

  • 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.
  • All valves shall be accessible for maintenance.
  • All service fixture controls (e.g. gas, air, water, vacuum) shall be external to the fume hood, clearly identified and within reach.
  • All service fixtures within the workspace shall be corrosion resistant or have a corrosion resistant finish.
  • If water service is provided, the fume hood shall have provisions for a suitably designed drain.
  • 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.
  • Light fixture(s) mounted inside the fume hood liner shall be protected against corrosion.
  • Light fixture(s) mounted inside the fume hood liner shall be vapour proof.
  • Light fixture(s) shall be capable of providing an illuminance luminance at the work surface consistent with the level required by Part VI of the Canada Occupational Safety and Health Regulations.

Alarms

  • A fume hood shall have an audible and visual alarm to indicate to the user when the air flow deviates from the set point.
  • The alarm shall be readily visible to the user during use of the fume hood.
  • Only authorized personnel shall be able to adjust the alarm set point.
  • The alarm shall remain functional in the event of loss of mains electrical power.
  • 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

  • Exhaust ducts should be constructed to SMACNA Seal Class B Standards as a minimum.
  • Exhaust ducts should be maintained under negative pressure.
    • 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.
  • Fume hoods with integral fans shall have appropriately constructed exhaust ducts.
  • 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.
  • 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.
  • The exhaust stack shall not be fitted with devices, which deflect the effluent or reduce the discharge velocity.
    • Rain protection by weather caps and swan neck ducts are examples of such devices.
  • Thermoplastic materials shall not be used for duct work.
  • Fire-retardant material or carbon steel with an acid-resistant coating may be used for general chemical applications.
  • Stainless steel ducts shall be used for perchloric acid fume hoods.
  • Corrosion-resistant ducts shall be used for radioisotope fume hoods.
  • Vitrified clay pipes with sealed joints may be used for acidic, alkaline, and plating solutions

Exhaust fan

  • Exhaust fans should be positioned as close as possible to the termination (discharge end) of the duct, preferably on the roof. Note: 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.
  • 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.
  • Glass fibre, PVC, or equivalent fans shall be used for highly corrosive conditions.
  • Coated steel, glass fibre, or PVC fans may be used for low to moderately corrosive conditions.
  • 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.

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:

  • 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.
  • All exposed parts of the fume hood interior shall be suitable for use with perchloric acid.
  • The work surface shall be watertight and furnished with a raised lip to contain spills and wash down water.
  • 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.
  • The duct work shall be self-draining with no horizontal sections.
  • 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.
  • The baffle shall be removable to allow periodic inspection for damage/corrosion.
  • The fume hood shall be constructed of nonporous, inorganic, acid-resistant, non reactive material, and shall be impervious to perchloric acid.
  • Specially designed fans shall be used.

Installation

Location

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

  • Fume hoods should be located out of the normal, traffic pattern and away from interfering room air currents.
  • Seated work stations shall not be located directly opposite fume hood openings.
  • 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
    Note: The adjoining wall may present a partial obstruction which may affect intake air flow.
  • The user's unobstructed personal work area should extend at least 1.5 m from the face of the fume hood.
  • 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.
  • 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.
  • The distance between the sash of the fume hood and a doorway should be at least 1.5 m.
  • The distance between the side of the fume hood and a doorway should be at least 1.0 m
  • 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

  • The exhaust duct should be self-draining and proceed to the discharge point with as few horizontal sections as possible. This is to minimize areas in which condensates or liquids coming in from the discharge point can collect.
  • Ducts shall be sealed, according to SMACNA Seal Class B Standards, to prevent leakage
  • 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
    • 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:

  • Electrical safety
  • Adequate lighting
  • Noise level (less than 55 dBA)
  • The functioning of components and services
  • Field performance test results as specified in Clause 11.4 CSA Z316.5-94

Field test

  • All test and measurement equipment shall be accurate and properly calibrated as specified by the manufacturer and relevant Standards.
  • 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.
  • 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.
  • 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.
  • The sash is open to a normal working height (approximately 18").
  • The minimum face velocity is between 100 to 120 fpm.
  • The maximum sash working height is marked.

Sash operation

  • Sash operation shall be smooth and easy throughout its travel.
  • Sash(es) shall be operable from either end with one hand.
  • Sash counterbalances should operate without interference or restriction.
  • Vertical rising sashes shall hold at any set height without creeping up or down.
  • All adjustable baffles shall operate freely, 'without binding or restriction.
  • 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. 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:

  • Inspect the fans, motors, drives, and bearings for correct operation.
  • Test the controls of the services to the fume hood for proper operation.
  • Inspect the fire damper and the release mechanism.
  • Measure the fume hood face velocity and compare to fume hood specifications, correct as necessary.
  • Test the operation of the air flow alarm.
  • Repair defects and lubricate as necessary.

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Glassware

Glassware is used in almost every type of chemical and biological lab. Depending on the processes being performed, specific safety precautions should be taken to reduce breakage and implosions.

General safety tips for using glassware
  • Borosilicate glass (e.g.. Pyrex, Kimax) should be the only type of glass used in the lab for any processes requiring heat or pressure. Soft glass should only include reagent bottles, measuring equipment, stirring rods and tubing. Exceptions may include experiments requiring UV or other light sources.
  • Glassware should be inspected prior to each use to ensure that cracks, chips or other defects are not present.
  • Glassware that is to be used in evacuated processes should be heavy-walled and covered with fabric-backed (i.e.. duct) tape or plastic mesh to prevent flying glass should an implosion occur.
  • Glass tubing and stirring rods that have been cut to size should be fire-polished prior to use to remove sharp edges that can cause a laceration to a worker, or to tubing, stoppers or other soft materials.
  • Be sure to cool hot glass slowly after polishing. Quick-cooling can cause weaknesses in glass that may cause it to break when reheated or pressurized.
  • When inserting glass tubing into a rubber stopper:
    • Always lubricate the stopper hole with water or preferably glycerine first.
    • Hold both tubing and stopper with thick cloth or gloves, less than 5 cm from the point of insertion.
    • Push the tubing into the stopper by applying slight pressure and a gentle twisting motion.
    • Never try to pull out glass tubing stuck in a rubber stopper or tubing. Cut the stopper or tubing instead.
  • Glassware should be cleaned with care to avoid breakage that can cause lacerations. Never clean broken glass out of a drain by hand - use tongs or forceps.
  • Store glassware on shelves with a lip or a closed cupboard, and don't stack glassware.

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Heating baths

Often materials used in heating baths are flammable and excessive temperatures could result in a fire. 

  • DO NOT LEAVE ON OVER NIGHT.
  • Heating bath containers should be durable, non-breakable, and set up with a firm support so they will not tip over.
  • Do not place heating baths near either flammable or combustible material.
  • Move heating baths only when the liquid is cool, to avoid risk of burning.
  • Set the thermostat well below the flash point of the heating liquid in use.
  • Keep a thermometer placed in the bath at all times it is in use to provide a visual indication of the actual temperature of the bath.

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Heating mantles

Heating mantles are composed of an electrical element surrounded by layers of fiberglass. These are generally safe pieces of equipment, provided the following:

  • Ensure that the coating around the fiberglass is not worn or broken and that no electrical components are exposed. It is also advisable to ground the outer metal case to protect against an electric shock if the heating element inside the mantle shorts against the metal case. 
  • Always use a heating mantle with a variable autotransformer (VIAT) to control the input voltage. Never plug them directly into a 110-V line.
  • Be careful not to exceed the input voltage recommended by the mantle manufacturer. Higher voltages will cause it to overheat, melt the fiberglass insulation and expose the bare heating element.

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Ovens

Ovens are used in laboratories for baking or curing materials, out-gassing, removing water from samples, drying glassware, or in some cases providing a controlled, elevated temperature for an experiment. Follow these guidelines:

  • Equip every oven with a back-up thermostat or temperature controller which will either control the unit or shut the oven down should the primary one fail.
  • Do not use a unit with only a single thermostat for long, unattended processes. A backup system should be used in case the first thermostat fails.
  • Do not use an oven to heat any material from which a toxic vapour or gas would be expected to evolve unless provisions are made to exhaust the fumes, as would be done with a fume hood.
  • Do not use mercury thermometers in ovens.

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Refrigerators and freezers

Refrigerators and freezers used for chemical storage must have signs indicating their purpose.

Food and beverages are not permitted in a refrigerator containing chemicals.

To reduce odour build-up in a refrigerator seal all containers tightly and wipe any spilled material from the container prior to storing in the refrigerator. All containers must be clearly and legibly labelled (i.e. WHMIS labels).

Approved equipment

Refrigerators/freezers must be CSA certified and in the case of explosion-safe refrigerators must also be UL listed. Converting domestic units into flammable storage units is not permitted at UW.

Chemical storage

Non-flammable chemicals

Domestic refrigerators/freezers are suitable for storage of non-flammable chemicals.

Flammable chemicals

Laboratory explosions have resulted when ordinary domestic refrigerators have been used for storage of flammable liquids, and leaking vapours have reached one of the many ignition sources within such refrigerators.

Domestic refrigerators/freezers are not be used to store flammable liquids. Any uncertified refrigerators/freezers need to be replaced no later than July 1, 2015. You can contact the Safety Office if you are uncertain of your situation.

Flammable chemicals requiring refrigeration must be stored in a refrigerator/freezer designed for the safe storage of flammables. Flammable liquids are defined by the Ontario Fire Code as having a flash point of less than 37.8 degrees Celsius.

Explosion-safe or laboratory-safe refrigerators/freezers must be used. These units have no electrical sparking devices, relays, switches, or thermostats that could ignite flammable vapours inside the cabinet. Flammable storage refrigerators may incorporate design features such as thresholds, self-closing doors, magnetic door gaskets, and special inner shell materials that control or limit the damage if a reaction occurred within the storage compartment.

Please note that the more costly explosion-proof refrigerators/freezers are not required in labs at UW (unless the refrigerator/freezer is in a location where there is a volatile atmosphere such as a solvent dispensing room). These units are similar in design to the explosion-safe units, but also have all operating components sealed against entrance of explosive vapours. Electrical junction boxes are also sealed after connections are made.

Service, repair and disposal

Refrigeration equipment is to be serviced by a person certified under the regulation (Environmental Protection Act).

Refrigeration equipment can be disposed of only after the refrigerant has been removed and the equipment tagged by a person certified under the regulation.

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Rotary evaporators

Evaporation by using a rotary evaporator is the most common method used to separate a solvent. These are often known as "rotovaps", and operate by placing a flask under a vacuum while heating and spinning it. This allows solvent to evaporate more quickly.

Guidelines for operating a rotary evaporator
  • Use Pyrex or similar glass, enclosed in safety mesh to prevent flying glass in case of implosion. Inspect all glassware prior to use.
  • Wear proper personal protective equipment including lab goggles, protective clothing and gloves.
  • Use a safety shield over the flask, which provides a physical barrier to flying glass in the case of implosion.
  • Apply the vacuum slowly.
  • Use a solvent trap to keep solvents out of vacuum pump or drain if using a vacuum aspirator.
  • Maintain temperatures of less than 180°C.
  • Do not use a heating source other than water or oil bath.
  • Use plastic clips to secure glassware.

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Solvent stills

Solvent stills are used to purify flammable liquids into pure, dry solvent. If safety precautions are not observed, a solvent still is very dangerous. The chemicals used in solvent stills are air/water-reactive and flammable, and pose a significant risk of serious injury and damage due to fire if not handled properly. Deactivation/neutralization procedures are particularly sensitive. All workers in the lab should be trained on the general hazards of solvent stills, and users must be trained and competent in all aspects of use.

General solvent still safety procedures
  • Stills MUST be located inside fume hood.
  • Wear all required personal protective equipment (lab coat, goggles, face-shield and gloves).
  • Keep volume of solvents to a minimum.
  • Label all flasks with appropriate labelMercury-Containing
  • All flammable solvent stills must only be filled/re-filled when they are at room temperature. Electrical devices must be turned off in the fume hood and all heating devices such as mantles or hot plates must be turned off for at least 5 minutes prior to filling to avoid ignition of vapour.
  • Electricity must be controlled by a water flow switch which will turn off the electricity if the cooling water supply drops below a minimum safe flow rate.
  • Use an inert gas (nitrogen or argon) to keep solvent dry and free of oxygen. Maintain a steady stream of inert gas when neutralizing the still.
  • Stills must be vented, with bubbler to prevent pressurizing the system.
  • Use correct drying agent for each solvent.
  • Do not leave running solvent still unattended, especially overnight.
  • Neutralize stills either with another trained lab worker or a supervisor. Follow strict procedures for specific agents. Stills must be cleaned regularly to prevent accumulation of products that make it difficult to neutralize. Solvent can also erode the glass of the flasks they are heated in.
  • Keep a dry-chemical fire extinguisher nearby.

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Mercury-containing equipment and thermometers

Mercury thermometers have been banned at UW since 2015.

Follow these steps if your lab has mercury thermometers: 

  1. Bag them tightly
  2. Seal the bag
  3. Transport them to the waste facility during your normal waste drop-off

Contact esf@uwaterloo.ca if you have any questions. 

Mercury-containing equipment

Equipment that contains mercury should be placed in a secondary containment/tray, if possible, to contain any potential spills. If not possible, contact the Safety Office to develop a spill plan, in advance.

Mercury spills

If you have a mercury spill, the mercury itself is not an emergency. 

  1. Close off the area 
  2. Put a sign on the door
  3. Call the spills team via the Special Constables Service during regular office hours for help cleaning the spill

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