The probability of harm or damage from a hazard.
When you are working in a chemistry laboratory, there is a certain level of risk associated with each chemical you will be using.
Assessing the risks of hazards means thinking about:
- How you might be exposed to the hazard
- What would be the probable results of that exposure, should it occur
Risk assessment involves determining (estimating) the probability of some adverse event occurring. This means that you will need to be thinking about the upcoming work with this chemical in terms of how you might be exposed during preparations before the experiment, use during the experiment, and after the experiment.
After you assess the risks, the next step will be thinking about how you can minimize the risks of exposures (from the assessment) by using equipment or techniques or procedures to limit exposures. The following case example is for sodium hydroxide (NaOH); however, you should approach the use of any chemical in a similar manner.
- Assess the risks presented by the most important hazards.
- Use SDSs and the GHS Hazard Categories and Statements to determine the relative risk of the hazards.
- Check to be sure all glassware and equipment are in good shape and working condition.
Before an Experiment
- Know what you are working with.
You should always identify the substance you are working with and think about how you can minimize exposure to this in the experiment. For example, sodium hydroxide is commonly known as lye or caustic soda. If you are unsure, look for the Chemical Abstracts Service (CAS) Registry Number on the product label of the chemical and look it up online using reliable sources.
- Find and evaluate hazard information.
This information is typically found on the SDS, which suppliers are required to provide the end user. The label of the original container also contains valuable safety information. For sodium hydroxide (NaOH) as an example, the hazard information would include:
- The corrosive levels for the solid and for solutions. In the case of NaOH, corrosive means “able to burn or corrode organic tissue by chemical action”.
- The effects of exposure at varying concentrations; for example, 0.05 moles per liter (M) or less (may cause burns to eyes or open wounds), 0.05 M to 0.5 M (irritant to eyes and skin), and 0.5 M or greater (severe burns and may cause blindness if it comes in contact with eyes). The SDS, as with any chemical, gives information on the hazards.
- Ensure that the proper concentrations are prepared.
Students in a typical high school laboratory should not routinely work with basic (NaOH) or acidic (HCl) solutions at concentrations greater than 1 M.
- Ensure that all chemical bottles are properly labeled.
In a high school setting, using sodium hydroxide as the example again, the bottle should have the chemical name (“sodium hydroxide”) spelled out, not just the formula (“NaOH”), and the concentration of the solution should also be listed. Additional information, such as signal words and words describing the specific hazards, should be on the label of the original chemical container. It is also recommended to add any GHS pictogram labels to secondary containers, as needed.
- The signal words “Danger”, “Warning”, and “Caution” are used to describe the level of the hazard.
- Words such as “Caustic”, “Corrosive”, and “Flammable” are used to describe specific hazards.
A Closer Look
What Graduate Students Should Know
Graduate students should be able to accurately assess the risks of specific hazards. As discussed previously, risk is the probability of suffering injury or harm from being exposed to unsafe chemicals, processes, or equipment.
Graduate students should be able to use various hazard rating systems to determine the relative severity of the hazards of a specific process, and to provide an accurate probability of exposure to these hazards under specific conditions.
Graduate students should be able to determine whether probability of exposure or severity of hazard is more important in a specific situation. For example, the probability of exposure might be considered first if there are no controls or protective measures—in this case, many hazardous chemicals can cause serious harm, injury, or even death.
During an Experiment
- Use the lowest concentrations and smallest volumes possible for all chemicals
Do not allow students to handle solids that are classified as fatal or toxic if swallowed
- Wear appropriate eye protection that offers both impact and splash protection
This is not only for your safety but also as a precaution in the event that an accident is caused by someone else in the laboratory
- Wear appropriate protective clothing (laboratory apron, coat, and gloves)
- Be certain that the reagent bottle and the container are properly closed after transferring a chemical (solid or liquid) from a reagent bottle into a secondary container
What if an Emergency Occurs?
Teachers must receive all necessary training in case of an incident or emergency. Normally, teachers should not provide medical treatment for students. However, in some cases the teacher may have to act before medical personnel arrive. The emergency training must include how to use an eyewash station and safety shower, for example:
- If the chemical is in the eye:
Flush water using an eyewash station for at least 15 minutes. Medical attention must be summoned as soon as possible.
- If the chemical is swallowed or ingested:
Do not induce vomiting unless the SDS recommends vomiting. Medical attention must be summoned as soon as possible.
- If the chemical comes into contact with skin:
Rinse the affected area for 15 minutes with tap water. It may be necessary to use a safety shower. If the safety shower is used, all contaminated clothing should be removed while the person is under the safety shower, and medical attention must be summoned as soon as possible.
After an Experiment
- Ensure that all chemicals are properly stored
Make sure that the caps on the reagent bottles are tightly secured
- Ensure that benches are clean before the next class comes in
One of the major causes of accidents is carelessness on the part of someone else