Safety Questions From Teachers 

If you have any safety related questions for our Safety Committee, please do not hesitate to submit your safety questions to


Question: Biofeedback body rhythms March 9, 2024

I would appreciate some clarification on the following: i) on page 14 of 2018 Safe ON Science:

“Never attempt investigations of biological feedback in which body rhythms (e.g., heartbeat or the electrical activity of the brain) are detected, amplified, and then used to influence existing rhythms.”

What activities this may refer to specifically? The policy seems to be being dictated based on this statement.

Answer: Response from STAO’s Safety Committee:

An example of an inappropriate activity involving body rhythms is using an EKG probe (available from common equipment supply vendors) to monitor the effect of a stimulant like caffeine in coffee, high-energy drinks, or nicotine products on a student’s heart rate. Inappropriate amounts or an unknown pre-existing heart condition could put the student at risk. This is the underlining rationale of the statement on page 14 of Safe ON Science. Other devices that could measure body rhythms include some smartwatch apps and glucose monitors. However, we are unaware of how brain activity could be measured or influenced with equipment commonly found in schools. Any attempt to alter brain or heart activity to amplify or influence outside of normal rhythms is too risky.

Activities involving the collection of human body data can be of great interest to students. However, teachers should be aware that some activities can make some students feel uncomfortable, embarrassed, or isolated due to, e.g., their athletic ability or body image concerns. Hence, it is essential that the teacher select activities that are safe, inclusive, adaptable, offer students choices, consider students’ social and emotional needs, and be aligned with board safety policies and procedures.

Here are a few activities with potential adverse physical or emotional outcomes to avoid:

  1. Measurements of BMI and the use of fat calipers or weigh scales could be embarrassing for students who struggle with body image.
  2. Strenuous physical activities, e.g., sprinting, may trigger asthma and other heart and respiratory complications.
  1. Fasting and diet restrictions (e.g., studying the effect of a high carbohydrate diet) are inappropriate because students may be undergoing growth spurts or have other unknown nuritional needs.
  1. Using hyperventilation to alter breathing rates can cause students to be lightheaded, fall, or pass out.STAO’s safety publications were written to inform and guide school boards, schools, and science departments in developing policies and procedures appropriate for their system. Furthermore, we recommend that the development of these policies and procedures be a collaborative and cooperative process in which school boards rely on the experience and judgment of classroom teachers. This results in policies and procedures that are often more effectively implemented than those developed in isolation.

The STAO Safety Committee continues to monitor trends in science education safety to confirm our safety publications, e.g., Safer Use of Chemicals (2019) and Safe ON Science (revised edition 2018), remain relevant and reflected in the curriculum. Regular updates of these publications are the focus of the upcoming safety committee work.


Question: What are restricted chemicals?

To prevent their criminal use, 10 chemicals have been identified by the Natural Resources branch responsible for compliance with the Explosives Act. They are:

Hydrogen peroxide, Nitric acid, Potassium chlorate, Sodium chlorate, Potassium nitrate, Sodium nitrate, Ammonium nitrate, Nitromethane, Potassium perchlorate, and a mixture of sodium nitrate and potassium nitrate.

Click here to read more


Question: The STAO Safe on Science document (2011) indicates that only class 1 and class 2 lasers are recommended for use in high school science classes. Many of the documents that I have examined indicate that Class 3A (old classification), now called Class 3R (new classification) is also safe unless viewed through an optical device. I respectfully request that the safety committee re-examine this issue, and include Class 3R in the recommendation.


Answer: The Safety Committee Response:  Laser Classification: There are currently 7 hazard classes of lasers. As the class number increases, the danger from direct and indirect viewing of the laser beam increases.  1. Direct Viewing: While direct viewing may seem obvious, the eye must be in the path of the beam. High school activities typically position students at 90′ to the direction of the beam, as they watch it travel through lenses, reflect off mirrors, or form interference patterns when the beam enters a diffraction grating. Looking at a beam from the side as it travels through the air is not direct viewing and will not result in eye damage.  2. Indirect Viewing: Indirect viewing occurs through specialty devices that employ mirrors, lenses, and filters for detecting the laser beam.  Class 1, 1M, 2, and 2M lasers have a visible light beam, and are safe under normal conditions of use. The blink reflex will protect users from retinal damage if the light beam is accidentally shone in their eyes. However, viewing the beam through a microscope, binoculars, telescope or other optical equipment may cause immediate damage to the eye. Class 3R lasers can be either visible or invisible. They are also safe under normal conditions, and the blink reflex for a visible beam will protect users from damage if the beam is accidentally shone in their eyes. However, viewing the beam through a microscope, binoculars, telescope or other optical equipment may cause immediate damage to the eye. Class 3B and 4 are more powerful lasers. They can cause eye damage when viewed directly or by reflection from a matte or mirrored surface. Class 4 lasers also cause skin damage and may be a fire hazard. The Ontario Ministry of Labour requires that a Laser Safety Officer be appointed and trained to oversee the use of these types of lasers. Safety goggles specific to the laser wavelength must be worn when using these lasers.


Click here to read more!


Question: Can resonance rods do damage to a person’s hearing, especially if the demonstration is repeated several times during the day?

Tanya Malusev from Arbour Scientific measured the sound intensity. The maximum value achieved was 85 db. The frequency (not determined by them) occurs in a range of 2500 to 5000 Hz. OSHA indicates that habitual exposure to intensities can cause hearing damage. They published the following table:

8 hours at 90 db

4 hours at 95 db

2 hours at 100 db

0.5 hours at 110 db

The Canadian Centre for Occupational Health and Safety has also published a similar table listing sound intensity levels as they relate to hearing damage. As I interpret this, the resonance rods, while irritating (at this high frequency), will not do any damage to students/teachers at 85 db for such a short duration. This same interpretation was supported by Tanya (Arbour Scientific) in a personal email to me.

I hope that this information will be useful in making an informed decision as it relates to this particular demonstration. If new information is brought to your attention regarding this demonstration, I encourage you to share that with our committee. Please do not hesitate to contact us with further safety inquiries.

Click on the following link for a demo that illustrates the use of resonance rods!


Question: Recently, the safety of PTC paper, used widely for demonstrating the ability to taste vs the inability to taste PTC, has been called into question. Many school boards in the USA subsequently banned its use. Question: What is the perspective of the STAO Safety Committee with regard to the use of PTC paper as a student activity in Senior Biology?


Answer: The chemical in PTC paper is phenylthiocarbamide. It is also known as phenylthiourea. A quick look at an MSD sheet for this substance indicates that it is highly toxic, with an LD50 of 3mg/kg. OSHA has classified it as hazardous. The 2004  USA publication, Investigating Safety: A Guide for High School Teachers by Texley et al., suggested that the PTC content was high enough to be of concern. As a result, many school boards in the United States banned its use.

Dr. Steven Wooding is a research geneticist and is currently an Assistant Professor of Health at the University of California. Wooding et al. (2004) sequenced the coding region of TAS8R38 (detection of PTC) in 165 humans, one common chimp, and one gorilla. When asked to comment on the safety of PTC paper for the University of Utah, he stated that:

PTC is so intensely bitter that tasters can detect it in miniscule quantities. A single test paper from Carolina Biological Supply contains just 0.007 mg of PTC. And the amount that is licked off the paper by a test subject is much less than this.  Assuming a linear dose-response curve, we calculate that the 230 mg of NaCl in a vending machine bag of potato chips is about 100 times more toxic than the 0.007 mg of PTC in a taste paper.

STAO has published two documents (SOS and Safer Use of Chemicals)  where PTC paper was listed as toxic and not recommended for use. Instead, STAO suggests using sodium benzoate as a safer alternative. If it tastes salty, bitter, or sweet, then you are either homozygous dominant or heterozygous. If you do not taste sodium benzoate, then you are recessive.

Click here to read more!


Question: Should teachers be trained on fire extinguisher use?


Answer: STAO does not have a position as regards this training, nor is it required by regulation. There are some organizations (National Research Council in their book, Prudent Practices in the Laboratory) that suggest that this training should occur. The decision to train or not rests with the Joint Health and Safety Committee, and the School Board (employer).


Question: Are there any videos that are available for training on the use of fire extinguishers?

Answer: Yes. There are several youtube training videos that are available. Some of these are produced by reputable organizations (Fire Training Facilities, Fire Chief Associations, and Municipal Fire Departments). STAO does not specifically endorse these videos. The decision to use these rests with the school board (employer) and the Joint Health and Safety Committee. These are three links to videos produced by the Markham Fire Department.The first is specific to maintaining fire extinguishers. (3.5 min long) The second one on the list is specific to their use. It is very short, 44 sec long. The third on the list is captioned and has a commentator who uses American Sign Language to relay the message contained in the captions. It describes fire extinguisher use. (3.5 min)



 Markham Fire Videos

The link to the video below was produced at a State Fire Training Facility in Arizona. This facility was listed by the Arizona Fire Chiefs Association, affiliated with the National Fire Protection Agency (NFPA). It is detailed, covering fire extinguisher types, and how to use a fire extinguisher.(18.5 min)


Click here to read more!



Question: Are ductless fume hoods a good alternative to traditional fume hoods?

Since the summer, we’ve been taking an inventory of the fume hoods in our secondary schools and sending in an inspector to look at them.  We’ve found a few schools with no working hoods.  Given the infrastructure and energy demands of the built-in ones, we were thinking of purchasing ductless ones, like those outlined in the attached brochure.

Our Health and Safety department is concerned that these may be in violation of some of our codes (see below).  Has STAO come across any of these ductless hoods in Ontario schools and/or have any thoughts of their effectiveness?

Answer: I have read through a 2006 safety review regarding ductless fume hoods. The review was conducted by a committee at the National Institute of Health (NIH), and referenced a previous study by the Occupational Health and Safety Branch (DOHS) 1998. I have also consulted two other sources, Princeton University website and the reference textbook, Prudent Practices in the Laboratory (2011).


Click here to read the NIH review!



Question: I was at a school that had an externally vented flammable cabinet.  The cabinet at my current school isn’t vented and there is always a strong (somewhat overpowering) smell whenever the cabinet is opened.  While the MSDS sheet for methanol recommends use in a vented area, the storage requirements are only the use of a flammable cabinet.

I had the board’s safety officer to the site and he questioned the purchase of larger containers (1 L sizes) of alcohols and the presence of a large metal 10 L ethanol container.  He said the problem was with an overly filled cabinet and suggested that we dispose of our chemicals and just buy smaller quantities.  I tried to argue that this really doesn’t change the VOC nature of the chemicals.


Does STAO recommend the use of a vented flammable cabinet?

The advice from your safety officer is consistent with the STAO policy regarding the storage of chemicals. In our document Safe ON Science (2011), it is suggested that chemical inventories be reduced to include only those chemicals that are required. These should be purchased in quantities that can be consumed within a two to three year time frame. In our archives (Crucible 1994) in an article on flammable cabinet ventilation, the following sound advice was given:

For practical reasons in high schools, it is recommended that  (flammable liquids) quantities for no more than one year’s consumption, dated on receipt, be stored. The more the hazards of a liquid, the less the quantities that should be on hand. These liquids do not only present a problem in storage and use, but also in disposal of surpluses, or products of reactions. The less the frequency of use of a flammable liquid, the smaller should be the quantity to be stored.

As time goes on, the caps and sealer inserts become compromised and the liquids evaporate contributing to the vapours that come out of the  cabinet when it is opened. Ordering fresh new chemicals in smaller quantities regularly, while more expensive, reduces the  accumulated vapours. Removing chemicals that are seldom, if ever, used can also reduce the vaporous content of the flammables cabinet.

The National Research Council, in their book Prudent Practices in the Laboratory (published 2011 pp 239,240), has described two view points:

One view is that all such cabinets should be vented by using an approved exhaust system, because it reduces the concentration of flammable vapours below the LEL inside the cabinet. No fuel will be rich enough in vapour to support combustion. The other view is that in most circumstances flammable-liquid storage cabinets should not be ventilated. With a source of fuel and fresh air in vented cabinets, all that is needed is ignition for a fire to be started. Both views are valid.

VIEW ONE: In addition to reducing chemical inventories, and the quantities of chemicals stored, STAO does recommend the use of vented flammable cabinets. This reduces the exposure of teachers to vapours in the chemical storage area. For this reason, there also should not be any work stations or offices in this area.

VIEW TWO: The Ministry of Education (email received 2014), in compliance with Ontario Fire Code, requires that each school develop its own fire safety plan. This plan has to have the approval of local fire department officials. Local fire department officials approve ventilated cabinets in some districts, and do not approve them in others. Example: In my particular district, the ventilation of cabinets is not approved as it can cause a chimney effect during a fire.

Click here to read more, including requirements for installing venting.