Chapter 3
Laboratory Safety Equipments
A critical aspect of working safely with hazardous materials is the proper selection and use of different safety equipments such as personal protective equipments (PPE), fire safety equipments and fume hoods. All safety equipments should be carefully selected to ensure that it is appropriate for the hazards present and that the users will be able to perform their.
Personal Protective Equipments
Personal protective equipment, or PPE, is designed to protect students and any person doing laboratory work from serious injuries or illnesses resulting from contact with chemical, radiological, physical, electrical, mechanical, or other workplace hazards. PPE includes a variety of devices and garments to protect all parts of the human body such as goggles for eye protection, shield for eye and face protection, gloves for hand protection, lab coat for body protection, earplugs for ear protection, shoes for foot protection, hard hat for head protection and respirators for respiratory system protection.
The need for PPE is dependent upon the type of laboratory works and the nature and quantity of the materials in use, and must be assessed on a case by case basis. Laboratory Workers who rely on PPE must understand the functioning, proper use, and limitations of the PPE used.
Eye and face protection:
Thousands of people are blinded each year from work related eye injuries. Injuries that could have been prevented, if only people would have used eye or face protection.
The major types of accidents that cause blindness inside a laboratory include:
- Objects striking the eye;
- Contact with chemicals and other hazardous materials - Viewing radiant energy sources such as lasers.
Toxic chemicals in the form of gases, vapors, and liquids can damage the eyes. So, always read the appropriate MSDS before working with any hazardous material. Also, some manufacturing processes produce hazardous gases, vapors and liquids. Always check with your supervisor or safety manager to learn the type of eye or face protection you should used in order to work safely.
Safety glasses
Safety glasses look very much like normal glasses buy have lenses that are impact resistant and frames that are far stronger than regular glasses. Safety glasses with proper impact and shatter resistance will be
marked "Z87" on the frame or lens. Safety glasses must have side shields and should be worn whenever there is the possibility of objects striking the eye, such as particles, glass, or metal shards. Many potential eye
injuries could be avoided by wearing safety glasses. Safety glasses do not provide adequate protection from significant chemical splashes. They do not seal to the face, resulting in gaps at the top, bottom and sides, where chemicals may seep through. Safety glasses are also not appropriate for dusts and powders, which can get by the glasses in ways similar to those described above. Safety goggles are best used for this type of potential exposure.
Chemical Splash Goggles
Chemical Splash Goggles should be worn when there is potential for splash from a hazardous material. Like safety glasses, goggles are impact resistant. Chemical splash goggles should have indirect ventilation so hazardous
substances cannot drain into the eye area. Some may be worn over prescription glasses. Goggles come in a variety of styles for maximum comfort and splash protection.
Face Shields
Face shields are in order when working with large volumes of hazardous materials, either for protection from splash to the face or flying particles. Face shields must be used in conjunction with safety glasses or goggles.
Contact Lenses
Contact lenses may be worn in the laboratory, but do not offer any protection from chemical contact. If a contact lens becomes contaminated with a hazardous chemical, rinse the eye(s) using eyewash and remove the lens immediately. Contact lenses
that have been contaminated with a chemical must be discarded.
Body Protection
In the lab, you need to protect your body by wearing appropriate protective clothing that resists physical and chemical hazards. Lab coats are appropriate for minor chemical splashes and spills, while plastic or rubber aprons are best for
protection from corrosive or irritating liquids. Disposable outer garments (i.e., Tyvek suits) may be useful
when cleaning and
decontamination of reusable clothing is difficult. Inappropriate clothing (such as overlarge lab coats or ties), skimpy clothing (such as shorts), torn clothing
and unrestrained hair may pose a hazard in the laboratory.
Hand Protection
Human hands are unique. No other creature in the world has hands that can grasp, hold, move, and manipulate objects like human hands. They are one of your greatest assets. And, as such, must
be protected and cared for. Coming into contact with caustic or toxic chemicals, biological substances, electrical sources, or extremely cold or hot objects can irritate or burn your hands. Hand protection start with good hygiene includes hand washing. Hand washing helps to remove germs and dirt from
your hands. Clean hands are less susceptible to infection and other skin problems such as contact dermatitis. When handling chemicals in a laboratory, disposable latex, vinyl or nitrile examination gloves are usually appropriate for most circumstances. These gloves will offer
protection from incidental splashes or contact. When working with chemicals with high acute toxicity, working with corrosives in high concentrations, handling chemicals for extended periods of time or immersing all or part of a hand into a chemical, the appropriate glove material should be selected, based on chemical compatibility.
This table gives an example of chemical compatibility chart which shows how each type of glove material listed performed in breakthrough time tests against some common chemicals. All breakthrough time tests are performed under strict laboratory test conditions.
Foot Protection
If you are at risk for foot injury at your laboratory, you should wear the appropriate protective footwear.
Safety footwear is designed to protect feet against a wide variety of injuries. Impact, compression, and puncture
are the most common types of foot injury.
Closed-toed shoes should be worn at all times in buildings where chemicals are stored or used. Perforated shoes, sandals or cloth sneakers should not be worn in
laboratories or where mechanical work is conducted. Such shoes offer no barrier between the laboratory worker and chemicals or broken glass.
Chemical resistant overshoes or boots may be used to avoid possible exposure to corrosive chemical or large quantities of solvents or water that might penetrate normal footwear (e.g., during spill cleanup). Leather shoes tend to absorb chemicals and may have to be discarded if contaminated with a hazardous material. Although generally not required in most laboratories, steel-toed safety shoes may be necessary when there is a risk of heavy objects falling or rolling onto
the feet, such as in bottle-washing operations or animal care facilities.
Respiratory Protection
Workers should use respirators for protection from
contaminants in the air only if other hazard control methods are not practical or possible under the circumstances. Respirators should not be the first choice for
respiratory protection in workplaces. They should only be used:
- when engineering or administrative controls are not technically feasible.
- while engineering controls are being installed or repaired.
- when emergencies or other temporary situations arise (e.g., maintenance operations).
Respiratory hazards can include airborne contaminants such as dusts, mists, fumes, and gases, or oxygen-deficient atmospheres. Well designed and maintained engineering controls are the preferred methods of controlling worker exposure to hazardous contaminants in the air. These control methods include:
• mechanical ventilation
• enclosure or isolation of the process or work equipment
• proper control and use of process equipment, and
• process modifications including substitution of less hazardous materials where possible.
Hearing Protection
The most common noisy equipment in the laboratories is ultrasonicators, but most laboratory equipment and operations do not produce noise levels that require the use of hearing protection.
People should wear a hearing protector if the noise or sound level at the workplace exceeds 85 decibels (A-weighted) or dB(A). Hearing protectors reduce the noise exposure level and the risk of hearing loss. Using hearing protection, such as earplugs, earmuffs or
hearing bands, can improve communication or provide comfort to you in a noisy environment.
Head Protection
Generally, in regular laboratories, there is no need for head protection, but if you are doing
any work and you are at the risk of head injury, wear an appropriate head protection.
Laboratory Safety Emergency Stations Eyewash Stations and safety showers
Eyewashes and safety showers were developed in response to the increased use of hazardous chemicals. Eyewashes and safety showers are emergency systems used in both public and private industry to protect an employee from injury in case of contact with hazardous chemicals, chemical compounds or fire. The four basic ways these safety systems are used include:
1. Dilution, which dilute the chemicals that are on the skin or in the eyes to a non-harmful
level.
2. Warming/cooling, which warm or cool the body or eyes because of
a change in
temperature due to chemical exposures.
3. Irrigation, which flush the chemicals out of the eyes or off the skin.
4. Extinguishment, which put out fires of clothing on the body.
The eyewash is a unit that supplies fluid to irrigate and flush the eyes.
Eyewash stations should be located inside any laboratory.
If you accidentally get something in your eyes, go directly to the eyewash station and flush your eyes with water for 15 minutes. Be sure to hold your eyes open with
your fingers and "look" directly into the water streams. “DO NOT RUB YOUR EYES” because rubbing your eyes may scratch or embed particles into your eyes. Once you have flushed your eyes with water, seek medical
attention immediately. Also, be advised that some chemicals are water reactive and become toxic when mixed with water. Talk with your supervisor or safety manager about the chemicals you will be using on your job. Be familiar with the MSDSs for all chemicals used in your job.
The emergency shower is “a unit that enables a user to have water cascading over the entire body.”
This unit is used for general irrigation of the body and although it can be used to rinse the face, the unit is not meant for flushing of the eyes.
Any laboratories using hazardous
materials must have an eyewash and safety shower within 3 meters (00 feet) or 10 seconds travel time from the chemical use areas. Eyewashes and safety showers should have plumbed drains and the flooring under them should be slip-resistant.
Fire Safety and Fire Extinguishers
Fire is the most common serious hazard that you could faces in a typical chemistry laboratory. While proper procedure and training can minimize the chances of an accidental fire, you must still be prepared to deal with a fire emergency.
If your clothing is on fire (and the floor is not), use the SDR technique (STOP, DROP and ROLL) on the ground to extinguish the flames. If you are within a few feet of a safety shower or fire blanket, you can use these
instead, but do not try to make it "just down the hall" if you are on fire. If one of your coworkers catches fire and runs down the hallway in panic, tackle them and extinguish their clothing.
The Fire Triangle
In order to understand how fire extinguishers work, you first need to know a little bit about fire. Four things must be present at the same time in order to produce fire: Enough oxygen to sustain combustion, enough heat to raise the material to its ignition temperature, some sort of fuel or combustible material, and the chemical, exothermic reaction that is fire.
Oxygen, heat, and fuel are frequently referred to as the "fire triangle."
Add in the fourth element, the chemical reaction, and you actually have a fire "tetrahedron." The important thing to remember is: take any of these four things away, and you will not have a fire or the fire will be extinguished.
Essentially, fire extinguishers put out fire by taking away one or more elements of the fire triangle/tetrahedron.
Fire safety, at its most basic, is based upon the principle of keeping fuel sources and ignition sources separate.
Classification of Fuels
Not all fuels are the same, and if you use the wrong type of fire extinguisher on the wrong type of fuel, you can, in fact, make matters worse. It is therefore very important to understand the four different classifications of fuel.
Class A - Wood, paper, cloth, trash, plastics Solid combustible materials that are not metals.
Class B - Flammable liquids: gasoline, oil, grease, acetone Any non-metal in a liquid state, on fire.
Class C - Electrical: energized electrical equipment As long as it's "plugged in," it would be considered a class C fire.
D Class D - Metals: potassium, sodium, aluminum, magnesium
Unless you work in a laboratory or in an industry that uses these materials, it is unlikely you'll have to deal with a Class D fire. It takes special extinguishing agents (Metal-X, foam) to fight such a fire.
Most fire extinguishers will have a pictograph label telling you which fuels the extinguisher is designed to fight. For example, a simple water extinguisher might have a label like the one below, indicating that it should only be used on Class A fuels.
Types of Fire Extinguishers
Air-Pressurized Water Extinguishers
APW stands for "air-pressurized water." APWs are large, silver extinguishers which are filled about two-thirds of the way with ordinary tap water, then pressurized with normal air. In essence, an APW is just a giant squirt gun.
APWs stand about 2 feet tall and weigh approximately 25 pounds when full. They are designed for Class A (wood, paper, cloth) fires only.
POINTS TO REMEMBER ABOUT WATER EXTINGUISHERS
Never use water to extinguish flammable liquid fires. Water is extremely ineffective at extinguishing this type of fire, and you may, in fact, spread the fire if you try to use water on it.
Never use water to extinguish an electrical fire. Water is a good conductor, and there is some concern for electrocution if you were to use water to extinguish an electrical fire. Electrical equipment, including computers, must be unplugged and/or de-energized before using a water extinguisher on it.
Carbon Dioxide Extinguishers Carbon Dioxide extinguishers are filled with non-flammable carbon dioxide gas under extreme pressure. You can recognize a CO2 extinguisher
by its hard horn and lack of pressure gauge. The pressure in the cylinder is so great that when you use one of these extinguishers, bits of dry ice may shoot out the horn.
CO2 cylinders are red and range in size from 2 kg to 45 kg or larger. In the larger sizes, the hard horn will be located on the end of a long, flexible hose.
CO2s are designed for Class B and C (flammable liquid and electrical) fires only.
Carbon dioxide extinguishes work by displacing oxygen, or taking away the oxygen element of the fire triangle. The carbon dioxide is also very cold as it comes out of the extinguisher, so it cools the fuel as well. CO2s may be ineffective at extinguishing Class A fires because they may not be able to displace enough oxygen to successfully put the fire out. Class A materials may also smolder and re-ignite.
CO2s will frequently be found in laboratories, mechanical rooms, kitchens, and flammable liquid storage areas.
All CO2 extinguishers at USC undergo hydrostatic testing and recharge every five years.
Dry Chemical Extinguishers
Dry Chemical Extinguishers come in a variety of types. You may see them labeled:
"DC", short for "dry chemical",
"ABC" indicating that they are designed to extinguish class A,B,and C fires,
"BC" indicating that they are designed to extinguish class B and C fires.
Usually, "ABC" fire extinguishers are filled with a fine yellow powder. The greatest portion of this powder is composed of monoammonium phosphate. Nitrogen is used to pressurize the extinguishers.
ABC extinguishers are red and range in size from 2 kg to 9 kg on campus.
It is extremely important to identify which types of dry chemical extinguishers are located in your area.
Read the labels and know their locations! You don't want to mistakenly use a "BC" extinguisher on a Class A fire, thinking that it was an "ABC"
extinguisher.
An "ABC" extinguisher will have a label like this, indicating that it may be used on class A,B, and C fires.
Dry chemical extinguishers put out fire by coating the fuel with a thin layer of dust, separating the fuel from the oxygen in the air. The powder also works to interrupt the chemical reaction of fire, so these extinguishers are extremely effective at putting out fire.
These extinguishers will be found in a variety of locations. New buildings will have them located in public hallways. They may also be found in laboratories, mechanical rooms, break rooms, chemical storage areas, offices, university vehicles, etc.
Dry chemical extinguishers with powder designed for Class B and C fires may be located in places such as commercial kitchens or areas with flammable liquids.
Rules for Fighting Fires
Fires can be very dangerous and you should always be certain that you will not endanger yourself or others when attempting to put out a fire.
For this reason, when a fire is discovered:
SOUND THE ALARM. If you discover or suspect a fire, sound the building fire alarm. If there is no alarm in the building, warn the other occupants by knocking on doors and shouting as you leave.
LEAVE THE BUILDING. Try to rescue others only if you can do so safely.
Move away from the building and out of the way of the fire department.
Don't go back into the building until the fire department says it is safe to do so.
CALL THE SAFETY AND FIRE DEPARTMENT:
Total and immediate evacuation is safest. Only use a fire extinguisher if the fire is very small and you know how to do it safely. If you can't put out the fire, leave immediately. Make sure the fire department is called -- even if you think the fire is out. However, before deciding to fight the fire, keep these rules in mind:
NEVER FIGHT A FIRE IF:
1- You don't know what is burning. If you don't know what is burning, you don't know what type of extinguisher to use. Even if you have an ABC extinguisher, there may be something in the fire which is going to explode or produce highly toxic smoke. Chances are, you will know what's burning, or at least have a pretty good idea, but if you don't, let the fire department handle it.
2- The fire is spreading rapidly beyond the spot where it started. The time to use an extinguisher is in the incipient, or beginning, stages of a fire. If the fire is already spreading quickly, it is best to simple evacuate the building, closing doors and windows behind you as you leave.
3- Your instincts tell you not to. If you are uncomfortable with the situation for any reason, just let the fire department do their job.
The final rule is to always position yourself with an exit or means of escape at your back before you attempt to use an extinguisher to put out a fire. In case the extinguisher malfunctions, or something unexpected happens, you need to be able to get out quickly, and you don't want to become trapped. Just remember; always keep an exit at your back.
How to use a fire Extinguisher
It's easy to remember how to use a fire extinguisher if you can remember the acronym PASS, which stands for Pull, Aim, Squeeze, and Sweep.
Pull the pin. (This will allow you to discharge the extinguisher).
Aim at the base of the fire. (If you aim at the flames (which is frequently the temptation), the extinguishing agent will fly right through and do no good. You want to hit the fuel.)
Squeeze the top handle or lever. (This depresses a button that releases the pressurized extinguishing agent in the extinguisher).
Sweep from side to side until the fire is completely out. Start using the extinguisher from a safe distance away, then move forward. Once the fire is out, keep an eye on the area in case it re-ignites.
Common mistakes when putting off fires with fire extinguishers:
1- Standing against the air current, which decrease the fire extinguisher efficiency and expose you to heat and smoke.
2- Fail to direct the fire extinguishing material to the base of the fire.
3- Start using the fire extinguisher at a distance which is far away from the fire.
4- Not being sure that the fire is finished completely, which make a chance for the fire to start again.
Fire blanket
A fire blanket is designed to smother a fire by cutting off its oxygen supply. With no oxygen to feed it, the flames will die. Fire blankets were
once used to smother fire on humans, but not so much any more. A fire blanket is now more appropriate for smothering equipment fires, such as computers. A fire extinguisher would completely trash a computer if used. A fire blanket might salvage some computer parts.
Chapter 3 Questions
1- Define Personal Protective Equipments and explain its importance?
2- Explain briefly what you could use to protect:
a) eye b) face c) hand d) foot
e) reparatory f) hearing
2- How many Laboratory Safety Emergency Stations should be present inside a lab? Give examples.
3- How each of the following Laboratory Safety Emergency Stations Work:
a) eyewash Stations b) safety showers c) Fire Extinguishers 4- What should you do if your clothing is on fire?
5- Define the fire triangle and fire tetrahedron? How could you use any of them to put off fire?
6- Write down the different Classes of Fuels?
7- Explain the different types of Fire Extinguishers? Give examples?
Explain the suitability of each type to different classes of fuel?
8- Explain the following types of fire extinguishers:
a) DC b) ABC c) APW d) CO2s 9- Explain the essential rules for fighting fires?
10- What should you avoid in the case of fire?
11- Explain how could you use a fire Extinguisher?
12- What is the fire blanket and how could you use it?
