Module 4 - Laboratory hazards

Flammable materials are those with flashpoints below 37.8°C (100°F). Combustible materials are those with flashpoints at or above 37.8°C (100°F) and below 93.3°C (200°F). These materials are ever‑present, so much so that we may not even realize it. Examples include commercial-grade solvents, paint thinners, cleaning supplies, adhesives or glues, paints, waxes and polishes – and these don’t even include common laboratory products like acetone and methyl alcohol. General use requirements for flammable materials include: 

• Using flammable and combustible liquids within a properly functioning fume hood
• Ensuring that all sparking equipment (e.g., switches, relays, thermostats) are removed from the fume hood
• Ensuring pressure release valves open when heating flasks of flammable liquid
• Not heating flammable liquids with paint stripper guns
• Adding boiling chips to boiling liquids to prevent bumping
• Minimizing volumes to be heated, where possible
• Being prepared for a fire (proper extinguisher nearby, knowing evacuation route, etc.)
• Storing flammable materials in flammable storage cabinets

Pyrophoric materials are spontaneously combustible in normal atmospheres and must be handled under inert atmospheres (i.e., in the absence of oxygen). The chemical agent tert-butyllithium, which ultimately led to the death of Sheri Sangji at UCLA as depicted in the video, is pyrophoric and requires strict usage procedures. Before using any pyrophoric material, your supervisor needs to ensure that all necessary precautions have been implemented. It is recommended to discuss these matters first with the health, safety and risk manager so that a robust risk assessment can be performed.

Oxidizing materials give off oxygen and promote combustion. An oxidizer introduced into a particular environment will combine chemically with other materials and increase the risk of fire or explosion, which is why these materials need to be stored separately from flammable materials. Common oxidizers include oxygen, chlorine and bromine.

The dose makes the poison. Everything is toxic at some concentration. Too much exposure to mercury can result in the same outcome as too much exposure to water… it just does not take a lot of mercury to be fatal, as you can see in the video. General procedures for toxic materials include:

• Minimizing exposures using hazard controls and risk mitigation measures
• Installing and maintaining automatic monitors and alarms
• Using proper eye, face, hand and body protection
• Being familiar with and ready to implement emergency procedures
• Practising good personal hygiene
• Decontaminating your workspace regularly

Reactive materials are unstable or highly reactive and can unexpectedly produce uncontrolled reactions such as explosions or fires. These materials require specialized work procedures in addition to those noted below.

• Buy only as much as you need for your immediate research needs.
• Date the container as soon as it is received.
• Date the container when it is first opened.
• Do not open a bottle past its expiration date.
• Do not handle or open a peroxide former if crystals or precipitates are present; contact the health, safety and risk manager to arrange for safe disposal. Make sure to dispose of these materials prior to their expiry date. Costs may apply for materials requiring special disposal (specific waste sites, material tested prior to disposal, etc.).
• Store peroxide‑forming materials away from heat and light. Examples of materials that form peroxides after prolonged exposure to air or light include ethers, tetrahydrofuran (THF), cyclohexene, p-Dioxane and cyclooctene.
• Regularly monitor containers for signs of instability (e.g., changes in colour, crystal formation, drying out).
• Store perchloric acid bottles in glass or ceramic trays.
• Store water‑reactive materials away from sources of water (including sinks, eyewashes and emergency showers).
• Plan experiments carefully and thoroughly.

The video summarizes a laboratory explosion that occurred at Texas Tech University in January 2010.

Corrosive materials chemically destroy exposed body tissues and will also damage metal surfaces. Prolonged exposure increases the severity of injury. These materials will generally begin with a tingling/burning sensation, but they start to cause damage as soon as they make contact. Dilute acids should also be washed off skin and clothing as quickly as possible. A dilute acid left on clothing may become more corrosive as the water evaporates, causing more serious burns. Corrosives can be either acids or bases and include substances such as hydrofluoric acid (HF), hydrochloric acid, sulphuric acid, acetic acid, nitric acid and sodium hydroxide. General safe work procedures for corrosive materials include:

• Storing corrosive materials in corrosive storage cabinets and in secondary containers
• Storing corrosive materials on lower shelves (but not under sinks)
• Segregating acids and bases with secondary containment
• Storing hydrofluoric acid in plastic (HDPE or Teflon) containers (if you are planning to use HF, please contact the health, safety and risk manager; additional safety information is required, and there are specialty spill and exposure kit requirements before work with HF can commence)
• Ensuring all containers are labelled
• Using proper eye, hand, body (and where necessary, respiratory) protection
• Always adding acid to water, never the reverse
• Carefully decanting corrosive materials
  • Concentrated acids/bases (directly from the bottle) should always be decanted in a fume hood.
  • Once an aliquot of concentrated acid is diluted (>6M), the acid can be removed from the fume hood for use on a benchtop (containers must be labelled in accordance with WHMIS requirements).
• Knowing that oxidizing acids react with flammables
• Knowing that acids react violently with metals to produce hydrogen gas (this can spray corrosives outside of the container and potentially cause an explosion)

Cryogenic liquids cause cold burns and frostbite. These materials have boiling points below -180°C (‑292°F). Common examples include liquid nitrogen (-195.8°C) and liquid oxygen (-182.96°C), as well as mixtures of dry ice and isopropanol, which are not quite as cold (-78°C). It is important to note that very small amounts of liquid produce a large volume of gas, which in sufficient volume will rapidly lower available oxygen in the immediate area, creating an oxygen‑deficient atmosphere (in elevators, confined work areas, etc.). Solid oxygen crystals can also form in liquid nitrogen traps attached to vacuum lines. General procedures for the handling of cryogenic materials include:

• Wearing insulated gloves when handling cryogenic liquids.

• Wearing safety glasses or a face shield and minimizing skin exposure when handling, transferring or filling vessels. Containers should be filled slowly and never beyond the maximum indicated level.

• Cryogenic liquids/solids are often used to make cooling baths (e.g., acetone/dry-ice [-78^oC], liquid-nitrogen/acetone [-98^oC]). Once you are done using a cooling bath, you should allow for the solvent to degas (let the dissolved N₂ or CO₂ evaporate/sublimate) before either disposing of or storing the remaining solvent appropriately.
  • Never put a cryogenic in a closed system, as this will lead to a build-up of pressure and potential explosion.
  • Never put any cryogenics into or down a sink, as the temperature change and expanding gases can cause damage to both the sink and the piping.

Dewars for cryogenic materials – such as 200 L dewars for liquid nitrogen – are fitted with a pressure release mechanism. They will periodically vent through the pressure release valve, which can be quite startling and loud. This is a completely normal operation and is the result of boiling liquid nitrogen expanding within the dewar. The gas needs to go somewhere! Once the pressure is relieved within the dewar, the relief valve will close. Sometimes, the spring in the valve freezes open and needs to be doused in warm water in order to stop the dewar from venting.

There are two types of radiation – ionizing and non-ionizing materials. The Canadian Nuclear Safety Commission regulates the use of radioactive materials through a licence granted to the University. Strict procedural operations, training and monitoring are required to use these materials. Additional information on the radiation safety program is available online or from the Radiation Safety Specialist.

The use of biohazardous and infectious materials is regulated by the Public Health Agency of Canada and Health Canada. Strict procedural operations, training and monitoring are required to use these materials. See the additional information on the biosafety program or email the biosafety specialist.

The first three months of pregnancy are when the organs and limbs of an embryo/fetus form; this is the most sensitive period in its development. The University therefore encourages every pregnant worker to declare their pregnancy status as soon as possible to maximize their own safety and that of the future child.

Finding ways to control the possible risks found in the workplace, with the help of the supervisor, Health and Wellness and the health, safety and risk manager, is recommended. When possible, dangerous materials should be moved or replaced with less harmful substitutes. Safety precautions to minimize the risk of exposure to biological, chemical and physical agents should be reviewed with the supervisor, including the following general precautions:

• Do not smoke, eat or drink in laboratories.
• Never mouth pipette (i.e., do not use your mouth to transfer contents)
• Wash your hands after handling dangerous substances.
• Use the appropriate individual personal protective equipment:
  • Wear disposable, solvent‑resistant gloves (double up if necessary) to avoid all skin contact when handling dangerous substances.
  • Wear a lab coat or other protective clothing if there is a chance that substances will splash.
• Avoid transporting any residues of toxic substances on clothing, shoes, skin, etc. and contaminating other people, such as family members, particularly young children.

The pregnant worker or the supervisor is encouraged to advise the Health and Wellness Officer and the health, safety and risk manager so that they may be aware of the situation and assist with accommodating the worker. Confidentiality will be respected to the extent required by law.

Compressed gas cylinders pose multiple hazards, including the vessel itself. While the contents of the cylinder can be toxic, flammable or otherwise dangerous, cylinders are designed for the storage of these materials at high pressures, meaning that failure of the vessel can have catastrophic results.

General requirements for compressed gases:

• Cylinders must be properly secured. This means that they are secured either to a bench with a chain or strap at a point approximately two thirds of the way up the cylinder or in a clamshell base.

• Cylinders must be labelled like all other containers of hazardous materials. The cylinder supplier will normally already have labels affixed to the cylinder conforming to WHMIS and TDG requirements.
• Corroded lecture bottles and cylinders should not be stored or used.
• Connections (e.g., hoses, tubing and regulators) must be checked and verified upon connection to the cylinder and regularly thereafter.
• Cylinders marked as “empty” should be returned to the supplier as soon as possible. The return process should follow the procedure established within the faculty/service.
• When no longer in use or when in transport, valves must be closed, gas in the distribution lines and regulator must be purged, and the valve cap must be reinstalled. The cylinder must be stored in an approved storage location (e.g., a cylinder storage room). Laboratory space is not intended for cylinder storage.

Additional information is available in the compressed gas cylinder safety (PDF, 1.4MB) document.

Glassware (or reaction vessels) is seldom seen as a hazard. Normally, glassware does not present a hazard; however, glassware that is damaged or star-cracked can lead to serious consequences. Besides typical lacerations or cuts, contaminated glassware may introduce hazardous materials into the body. Additionally, microfractures in glassware under high pressure or vacuum may completely fracture, resulting in significant injuries or damage to infrastructure. Laboratory users are encouraged to:

• Inspect glassware for cracks, stars and stress lines before use (specifically when doing reactions/experiments that use either positive or negative pressure)
• Repair or discard defective glassware
• Wear eye protection when working with glass apparatuses
• Wear cut‑resistant gloves when inserting glass rods into rubber or plastic tubing
• Not wash broken glassware with other glassware
• Tape or enclose the reaction vessel on Schlenk lines
• Not mix glassware or broken glass with regular garbage

Lab equipment is purchased from all over the world, and each jurisdiction has different requirements for its use. For example, equipment purchased in Europe must conform to European standards and will be appropriate for their electrical systems. That same equipment may not be approved for use in Canada. When purchasing lab equipment, make sure to check that the electrical equipment (not just the peripherals) is suitable for use and certified by the Canadian Standards Association or the Electrical Safety Authority. Otherwise, this can lead to lengthy delays in releasing the equipment, as well as added costs in having it field‑certified by an appropriate electrical agency. Example markings are included below.

Mechanical hazards are not limited to manufacturing environments; they can occur within a laboratory space. Unguarded equipment, pinch points and in-running nip hazards can (and do) occur. Like all hazards, these too must be controlled. Properly guarded equipment will not permit access to moving parts.

In an all‑too‑tragic example, Yale University physics student Michele Dufault died in 2011 from accidental asphyxia due to neck compression when her hair became tangled in a piece of machinery in a lab. The accident occurred at 2:30 a.m. while she was working alone.

Ventilation – most laboratory work will be done in environments with general dilution ventilation systems having a minimum of six (6) air changes per hour. While helpful to reduce the extent of the hazard, dilution ventilation exhausts contaminants already made airborne. It is therefore critical to have auxiliary controls, such as local exhaust or fume hoods.

Local exhaust arms / snorkels – a point source, sometimes resembling an elephant’s trunk, capturing contaminants at (or very close to) the source of their generation.

Fume hood – a mechanically ventilated, partially enclosed workspace in which harmful materials can be handled more safely. Many fume hoods have alarms to indicate a potentially hazardous situation (e.g., inadequate face velocity), and all are inspected annually by Facilities. The following operational practices exist to ensure that the flow pattern within the fume hood is not disturbed (which could potentially lead to fumes escaping through the front of the fume hood):

• Avoid cross drafts when working in a fume hood.
• Keep the sash closed when not working in the fume hood.
• Do not obstruct back slots.
• Raise large pieces of equipment at least one inch above the floor of the fume hood.
• Set up the apparatus or sources of emission at least six inches behind the plane of the fume hood.
• Work with the sash at the indicated operating level.
• Never put your head into a fume hood.
• Fume hoods are not considered storage spaces; they are workspaces.

Using a smoke machine, the video shows how fume hoods are intended to contain the operations within their cabinet. A sash positioned too high will not maintain suitable face velocity, which will allow vapours to escape the containment of the cabinet and expose persons working nearby.

Glove box – a sealed container that is designed to allow a user to manipulate objects where a separate atmosphere is desired. Two types of glove boxes exist: one allows a person to work with hazardous substances, while the other allows the manipulation of substances that must be contained within a very high‑purity inert atmosphere. The Faculty of Science has additional information on glove box safety (PDF, 620KB).

Blast shield – a shield made of polycarbonate (or other solid material) with a weighted bottom, used as an additional layer of protection in experiments posing a risk of overpressurization or explosion. The shield is intended to absorb contact and protect the persons behind it.

Biological safety cabinet (BSC) – a primary containment device that protects the user and the immediate work environment from exposure to biohazardous material. BSCs come in three classes: Class I only provides personnel and environmental protection, while Class II and III also provide product protection. Class II BSCs are the most common BSCs used in microbiological laboratories.

Laminar flow hood – designed to provide product protection only, and should not be used when manipulating infectious material.

Labels and signage – under WHMIS, all hazardous products require identification consistent with the prescribed labelling requirements. Labels and signage may also be used to identify hazardous areas or serve as reminders to perform a particular task.

Alarms – signify potential danger associated with the substance they are monitoring. Advanced configurations may permit automated functions, such as stopping the flow of a process gas, at which point these administrative controls become engineering controls. Alarms are calibrated to a level well below the exposure or hazard level. Alarm activation provides early warning of a hazardous condition that may occur without intervention. Alarms are locally audible, and many are relayed to monitoring stations (such as Protection Services or Facilities).

Standard operating procedures – outline the work processes and how work is expected to be safely accomplished.

Authorizations – it is not enough to simply be trained for a particular project; one must also have the appropriate authorization to act.

Worker rotation – a reduction of time spent in a hazardous environment. For example, a worker may be able to spend less total time at a higher sound level and still be reasonably protected from the risk of hearing loss.

Protective eyewear – can be in the form of protective glasses (for impact), goggles (for splashes) and face shields (for impact / added protection). Protective eyewear must meet CSA standard Z94.3 (or equivalent).

Hearing protection – can be in the form of earmuffs or roll-down plugs. Hearing protection must meet CSA standard Z94.2 (or equivalent).

Lab coats – must be intended for chemical laboratory use (i.e., not a medical coat) and properly fitted to the arms (not dangling). A 100% cotton lab coat with snap-front closure is recommended.

Gloves – a variety of different types of gloves may be needed based on the work conducted. Disposable nitrile gloves are generally the most prevalent; however, breakthrough can easily occur with solvents. Latex rubber and thermal gloves are also commonly used.

Respiratory protection – can include N95s and tight‑fitting half‑ or full‑face pieces. Equipment must meet CSA standard Z94.4 (or equivalent) and must be selected following a hazard assessment. Learn more about respiratory protection (PDF, 1.63MB).