Safety Measures in the Laboratory

In Form 1 you learned the safety rules of the laboratory; this chapter covers the protective equipment you must know and use correctly p. 4. On 2 May 2018, 21 students and a teacher at a secondary school were quarantined for about 20 minutes after a broken thermometer spilled mercury in a science lab p. 3.

1.1 Personal Protective Equipment

Personal protective equipment is needed to protect the wearer from danger p. 4. On a student, it includes:

• Goggles, which protect the eyes from hazardous chemical substances such as acid, bromine, ammonia and reactive metals p. 4.
• A face mask, which protects the nose and mouth from inhaling pungent and volatile chemical substances and dust p. 4.
• Gloves made of rubber, which protect the hands from hazardous chemical substances p. 4.
• A lab coat, made up of safety layers and easily removed in an emergency, which protects clothing from damage p. 4.
• Closed shoes or safety shoes, which protect the feet from chemical substance spills and glass splinters p. 4.

The laboratory itself has a safety shower, an eyewash station, a fume chamber and a laminar flow cabinet p. 5. The safety shower rinses parts of the body or clothing, and the eyewash station rinses an eye, straight after contact with chemical substances p. 5. The fume chamber is for experiments with substances that are volatile, flammable, poisonous, corrosive or pungent, and the laminar flow cabinet avoids contamination during microbiological activities p. 5. Even with all this equipment, every accident or injury in the laboratory must be reported immediately to the teacher p. 5.

1.2 Disposal of Waste

Waste substances are of two types: those that can be disposed of into sinks and those that cannot p. 6. Only substances with low concentration that are non-hazardous, such as neutral substances, weak acids and weak alkalis, can go into sinks p. 6.

Substances that cannot go into sinks include solid waste, substances with a pH value lower than 5 or more than 9, organic solvent compounds, chemical substances such as acid, grease, oil, oil paint and hydrogen peroxide, toxic substances, heavy metals, organic waste such as microbes and carcasses, radioactive waste, and volatile and reactive substances p. 7. These substances can pollute the environment and are hazardous to living things p. 7.

Biological waste is managed with a Standard Operating Procedure (SOP) that sorts it into four categories p. 8. Sharp equipment (Category A) goes into sharps waste bins and is not autoclaved, non-sharp solids (Category B) are autoclaved, carcasses and organs (Category C) are frozen before disposal, and liquids such as blood and serum (Category D) are decontaminated by autoclave and then go into the sewage system p. 8. Category B waste is autoclaved in a leak-proof autoclave bag at 121°C and 15 psi for 20 minutes p. 8.

Accidents happen because of carelessness, negligence, events beyond expectation, or lack of skills or knowledge p. 9. Common ones are cuts from glass splinters, splashes of concentrated acid or alkali, small fires, contact with residue from reactive metals, broken thermometers, gas leaks and electric shock p. 9. A broken thermometer spills mercury, and mercury poisoning happens when someone touches it or it absorbs through the skin; mercury can attack the nervous system, digestive tract, reproductive system and kidneys p. 9.

1.3 Fire Extinguishers

A fire extinguisher is a device that is used to control or extinguish fire, and the four common types are classified by their medium p. 10. Each has its own label colour: water is red, foam is cream, carbon dioxide is black and dry powder is blue p. 10.

Fires are grouped into classes by the substance that burns, and the extinguisher is chosen for the fire sources found in a building or area p. 11. Dry powder suits every class, while a Class D fire in metals such as magnesium, aluminium, sodium and potassium can only take dry powder p. 11. Other options are the ABC fire extinguisher, the fire blanket, sand for an early-stage fire, and water for any fire except one resulting from oil p. 11.

To use a fire extinguisher, remove the safety pin and hold it upright, aim the nozzle at the base of the fire from around 2.0–2.5 metres, squeeze the handle, then sweep the nozzle from side to side over the whole fire p. 12. A home should keep one dry powder or ABC-type fire extinguisher p. 12.

A school audit of fire extinguishers records their types, expiry dates, pressure readings, the number of each type, and their locations on the school’s emergency route plan p. 13. In a STEM project, you design a simple fire extinguisher from materials found at home, because a kitchen holds flammable substances such as flour, sugar and oil p. 14.