Guidelines for Safe Laboratory Practices

It is highly recommended that all researchers read this material carefully.

Portions of this information are based on text written by Professor Rick Danheiser and colleagues in the Department of Chemistry, Massachusetts Institute of Technology.

Please familiarize yourself with Safety Guidelines and Environmental Health & Safety and Health Services at your university.

Always read the MSDS for any materials you work with, especially if you are unfamiliar with them. Search for MSDS’s here

Take additional precautions for work with flammable substances.
Flammable substances are among the most common of the hazardous materials found in campus laboratories. Flammable substances are materials that readily catch fire and burn in air. A flammable liquid does not itself burn; it is the vapors from the liquid that burn. The rate at which different liquids produce flammable vapors depends on their vapor pressure, which increases with temperature. The degree of fire hazard depends also on the ability to form combustible or explosive mixtures with air, the ease of ignition of these mixtures, and the relative densities of the liquid with respect to water and of the gas with respect to air.

An open beaker of diethyl ether set on the laboratory bench next to a Bunsen burner will ignite, whereas a similar beaker of diethyl phthalate will not. The difference in behavior is due to the fact that the ether has a much lower flash point. The flash point is the lowest temperature, as determined by standard tests, at which a liquid gives off vapor in sufficient concentration to form an ignitable mixture with air near the surface of the liquid within the test vessel. As indicated in the following table, many common laboratory solvents and chemicals have flash points that are lower than room temperature and are potentially very dangerous.

Flash Point (°C) Flash Point (°C)
Acetone -17.8 Ethanol 12.8
Benzene -11.1 Hexane -21.7
Carbon disulfide -30.0 Methanol 11.1
Cyclohexane -20.0 Pentane -40.0
Diethyl ether -45.0 Toluene 4.4

Precautions for handling flammable substances include:

  • Flammable substances should be handled only in areas free of ignition sources. Besides open flames, ignition sources include electrical equipment (especially motors), static electricity, and for some materials, (e.g. carbon disulfide), even hot surfaces.
  • Never heat a flammable substance with an open flame.
  • When transferring flammable liquids in metal equipment, static-generated sparks should be avoided by bonding and the use of ground straps.
  • Ventilation is one of the most effective ways to prevent the formation of flammable mixtures. A laboratory hood should be used whenever appreciable quantities of flammable substances are transferred from one container to another, allowed to stand or be heated in open containers, or handled in any other way. Be sure that the hood is free of all ignition sources including, in particular, variable transformers (variacs).
  • Generally, only small quantities of flammable liquids should be kept at work benches. Larger quantities should be stored away from ignition sources in flammable storage cabinets. It is advisable to purchase highly flammable solvents (e.g., acetone, hexane, diethyl ether, ethyl acetate, tetrahydrofuran) only in metal or break-resistant (e.g., plastic or plastic-coated), containers.
  • Refrigerators used for storage of chemicals must be explosion-proof or flame proof. Storage trays or secondary containers should be used to minimize the distribution of material in the event a container should leak or break.

Take additional precautions for handling highly reactive or peroxide forming substances.
Highly reactive substances are materials that decompose under conditions of mechanical shock, elevated temperature, or chemical action, with the release of large volumes of gases and heat. Special precautions are required for the safe use of highly reactive materials. It is the responsibility of the researcher to evaluate the reactive hazards involved in their work and to consult with their supervisor to develop detailed standard operating procedures for any work involving highly reactive substances. Work with highly reactive materials will generally require the use of special protective apparel (face shields, gloves, lab coats) and protective devices such as explosion shields and barriers.

Organic peroxides are among the most hazardous substances handled in campus laboratories. As a class, they are low-power explosives, hazardous because of their sensitivity to shock, sparks, and even friction (as in a cap being twisted open). Many peroxides that are routinely handled in laboratories are far more sensitive to shock and heat than high explosives such as Dynamite or trinitrotoluene (TNT), and may detonate rather than burn. All organic peroxides are highly flammable, and most are sensitive to heat, friction, impact, light, as well as strong oxidizing and reducing agents.

Many common solvents and reagents are known to form peroxides on exposure to air, and these chemicals often become contaminated with sufficient peroxides to pose a serious hazard. Classes of compounds that form peroxides by autoxidation include:

  • Aldehydes including acetaldehyde and benzaldehyde,
  • Ethers with primary and/or secondary alkyl groups, including acyclic and cyclic ethers, acetals, and ketals. Examples include diethyl ether, diisopropyl ether (especially dangerous!), dioxane, dimethoxyethane, tetrahydrofuran, ethyl vinyl ether and alcohols protected as tetrahydropyranyl ethers. Isopropyl alcohol also frequently forms peroxides upon storage.
  • Hydrocarbons with allylic, benzylic, or propargylic hydrogens. Examples of this class of peroxide-formers include cyclohexene, cyclooctene, methyl acetylene, isopropylbenzene (cumene), and tetralin (tetrahydronaphthalene).
  • Conjugated dienes, enynes, and diynes, among which divinylacetylene is particularly hazardous.
  • Saturated hydrocarbons with exposed tertiary hydrogens; common peroxide-formers include decalin (decahydronaphthalene) and 2,5-dimethylhexane.

Precautions for work with peroxide forming materials:

  • Store peroxide forming materials away from heat and light.
  • Protect peroxidizable compounds from physical damage, heat, and light.
  • Date peroxidizable containers with date of receipt and date of opening. Affixing a label stating “Warning, Peroxide Former” can also be helpful to alert others regarding these materials. Assign an expiration date if one has not been provided by the manufacturer.
  • Use or dispose of peroxides within time limits recommended on the label or MSDS. Before disposal you must test for peroxides and indicate the testing has been done and the level found (if any) on the red tag. If there is greater than 20ppm, a stabilization permit is required prior to shipment and final disposal.
  • Test for peroxidizables before distilling or evaporating peroxidizable solvents for research purposes. Do not distill for research purposes without treating to remove peroxides. It is illegal to evaporate or treat a regulated waste to avoid disposal of that material. All waste material should be disposed of properly.
  • If crystals are visibly present on the container or lid, or if the container is open but has not been tested, DO NOT OPEN, DO NOT TOUCH. Contact laboratory safety personnel to arrange for disposal.
  • Immediately rinse empty containers that once held peroxidizables. Do not let residues evaporate.

Take additional precautions for handling explosives.
Follow manufacturer’s instructions for handling and use of explosives.

Take additional precautions for work with corrosive substances.
Corrosivity is a complex hazard. Corrosives can be solids, liquids, and gases and includes acids, bases, oxidizers, as well as other chemical classes. Corrosives may belong to more than one chemical class. What is at risk varies, as well. Elemental mercury is considered a toxic substance, but it is shipped as a corrosive substance because it can deteriorate some metals. For purposes of these standard operating procedures, a corrosive is any chemical that can rapidly damage human tissue, metals, and other compounds, such as wood or concrete by chemical action. Store by compatibility. Segregate acids from bases. Segregate oxidizing acids, such as nitric acid from organic acids, such as acetic acid.

  • Store corrosives on a lower shelf or in ventilated corrosive storage cabinets.
  • Make sure containers and equipment, such as tubing, etc. used with corrosive materials is compatible with those materials.
  • Personal protective equipment is important for work with corrosives. Neoprene or rubber gloves, goggles and face shield, rubber apron, and rubber boots should be considered.
  • Always add acid to water, never water to acid.
    Wherever corrosives are used or stored, be sure there is a working, readily accessible eyewash and safety shower, and
  • Seek medical attention immediately in the event of a potentially injurious exposure.

Additional Procedures for Work with Particularly Hazardous Substances
Before beginning a laboratory operation, each researcher should consult the appropriate literature for information about the toxic properties of the substances that will be used.

The precautions and procedures described below should be followed if any of the substances to be used in significant quantities is known to have high acute or moderate chronic toxicity. If any of the substances being used is known to be highly toxic, it is desirable that there be at least two people present in the area at all times. These procedures should also be followed if the toxicological properties of any of the substances being used or prepared are unknown.

Establish designated areas in the laboratory for use of Particularly Hazardous Substances.
A key requirement of the OSHA Laboratory Standard is that all work with particularly hazardous substances be confined to designated areas. The designated area established in your laboratory depends on the circumstances of use for the PHS. A designated area may be the laboratory, a specific area of the laboratory, or a device such as a glove box or fume hood. There also may be designated equipment such as a specific balance, or centrifuge in which you work with or process PHS materials. It is most common for laboratory hoods to serve as designated areas for most research.

Make sure designated areas are posted with a yellow and black caution sign.
It is the responsibility of laboratory supervisors to define the designated areas in their laboratories and to post these areas with conspicuous signs reading “DESIGNATED AREA FOR USE OF PARTICULARLY HAZARDOUS SUBSTANCES–AUTHORIZED PERSONNEL ONLY.” In some cases it may be appropriate to post additional signs describing unusual hazards present and/or identifying the specific hazardous substances in use. You can also consider marking with yellow tape a section of a bench space or section of a lab hood where PHSs are used.

Use particularly hazardous substances only in the established designated areas.
Using PHSs outside of areas designated for their use, poses a significant danger to you and the others in your laboratory and surrounding areas.

Take action to prevent skin contact.
Contact with the skin is a frequent mode of chemical injury. Avoid all skin contact with particularly hazardous substances by using suitable protective apparel including the appropriate type of gloves or gauntlets (long gloves) and a suitable laboratory coat or apron that covers all exposed skin. Always wash your hands and arms with soap and water immediately after working with these materials. In the event of accidental skin contact, the affected areas should be flushed with water and medical attention should be obtained as soon as possible.

Avoid inhalation of PHSs.
Avoid inhalation of PHSs by ensuring that work involving potential for exposure to a gas, vapor or airborne dust is conducted in a laboratory hood, or other suitable containment device such as a glove box. Purchase material in liquid form rather that powder form when possible.

Thoroughly decontaminate and clean the designated area(s) at regular intervals.
Decontamination procedures should be established in writing, especially those involving chemical treatments, and consist of any necessary periodic (daily, weekly, etc.) procedures performed to control exposure of employees. Depending on the chemical material, this may consist only of wiping a counter with a wet paper towel, or periodic use of a neutralizing agent. To determine the proper decontamination procedures, one must consider the chemical (or type of chemical), the amount of chemical used, the specific use, the location of use, and other factors.

Be prepared for accidents.
The laboratory worker should always be prepared for possible accidents or spills involving toxic substances. To minimize hazards from accidental breakage of apparatus or spills of toxic substances in the hood, containers of such substances should generally be stored in pans or trays made of polyethylene or other chemically resistant material and, particularly in large-scale work, apparatus should be mounted above trays of the same type of material. Alternatively, the working surface of the hood can be fitted with a removable liner of adsorbent plastic-backed paper. Such procedures will contain spilled toxic substances in a pan, tray, or adsorbent liner and greatly simplify subsequent cleanup and disposal.

If a major release of a particularly hazardous substance occurs outside the hood, then the room or appropriate area should be evacuated and necessary measures taken to prevent exposure of other workers.

Don’t contaminate the environment.
Vapors that are discharged from experiments involving particularly hazardous substances should be trapped or condensed to avoid adding substantial quantities of toxic vapor to the hood exhaust air.

When necessary, restrict access to designated areas when particularly hazardous substances are in use.
Designated areas should be posted with special warning signs indicating that particularly toxic substances may be in use. As discussed above, many laboratory hoods are designated areas for work with particularly hazardous substances.

Additional Requirements for Work with Select Toxins
Select Toxins are biologically derived toxic chemicals that are specifically regulated by the federal U.S. Department of Health and Human Services under regulation 42 CFR Part 73 when handled at levels above specified quantities.

These materials are highly toxic and special precautions should be taken whenever handling concentrated forms, even in small amounts. Stocks of these chemicals should be stored under lock and key. An SOP should be maintained and accessible in the researchers’ laboratory space and should be provided to the Chemical Hygiene Officer.

Special Precautions for Work with Hydrofluoric Acid
Hydrofluoric acid (HF) is a particularly hazardous substance, like many acids, but has added dangers that make it especially dangerous to work with. HF is less dissociated than most acids and deeply penetrates the skin. Symptoms of exposure may be delayed for up to 24 hours, even with dilute solutions. HF burns affect deep tissue layers, are extremely painful, and disfiguring. The highly reactive fluoride ion circulates throughout the body and can cause multiple organ toxicity, including heart arrhythmias and death, if not treated. Any suspected exposure to HF should be immediately flooded with water, decontaminated with calcium gluconate gel, and treated by a medical professional.

Special Precautions for Work with Formaldehyde
Formaldehyde is a particularly hazardous substance that is widely used and is covered under a specific OSHA Standard 1910.1048. Labs must identify all laboratory activities that are above the OSHA action level or STEL through initial air monitoring and provide training, medical surveillance, and engineering and work practice controls if air levels warrant it.

Formaldehyde is an animal carcinogen and a suspect human carcinogen according to OSHA and IARC. It is also a sensitizer and can cause allergic skin reactions and asthma-like respiratory symptoms. It is an irritant to eyes, nose, and throat.

The Industrial Hygiene Program (IHP) has performed extensive air sampling for formaldehyde during a variety of lab activities such as animal perfusion, dissections, and tissue fixation and found the results to be below OSHA levels provided that suitable exhaust ventilation is used. Almost all formaldehyde procedures should be performed with ventilation such as a fume hood, slot hood, or vented downdraft table. All work should be done using gloves with adequate resistance to formaldehyde, such as the Best N-Dex brand (a disposable nitrile glove).

With proper exhaust ventilation, you should not detect any odors from formaldehyde work nor experience any symptoms of exposure such as eye tearing or throat irritation. Notify IHP for an evaluation if your procedures change and you work with large quantities of formaldehyde, perform animal perfusions, or do extensive tissue dissection work.

Special Precautions for Work with Nanomaterials
Nanomaterials are defined by the ASTM as a material with two or three dimensions between 1 to 100 nm. They can be composed of many different base materials (carbon, silicon, and metals such as gold, cadmium, and selenium). They can also have different shapes: such as nanotubes, nanowires, crystalline structures such as quantum dots, and fullerenes. Nanomaterials often exhibit very different properties from their respective bulk materials: greater strength, conductivity, and fluorescence, among other properties.

The toxicity of most nanomaterials is currently unknown. Preliminary toxicity testing has indicated that some nanoparticles may be more toxic than the corresponding micron sized particle because of their greater surface area and reactivity. Nano-sized titanium dioxide produces 40 fold more lung inflammation than micron-sized particles. In preliminary tests, carbon nanotubes have produced lung inflammation and fibrosis similar to crystalline quartz and asbestos. Nanoparticles are similar in size to viruses and are easily taken up by the body’s cells, translocate around the body, and can possibly pass into the brain and through the skin.

In the future, many types of nanoparticles may turn out to be of limited toxicity but precaution should be used until more is known. Work with nanoparticles that may release particles should be conducted in enclosures, glove boxes, fume hoods, and other vented enclosures. All work should be done with gloves, at a minimum disposable nitrile gloves.

This article also lists good reference sources for researchers to consult to keep up with toxicity information on their materials as it develops. Currently, nanoparticles and solutions containing them are being disposed of as hazardous waste.