Flammable solvents are defined as having a flash point of less than 100°F. Flashpoint is the minimum temperature at which a liquid forms a vapor above its surface in sufficient concentration that it can be ignited. Liquids with lower flashpoints ignite easier. Combustible liquids have a flashpoint at or above 100°F.

The National Fire Protection Association (NFPA) hazard classifications for flammable and combustible liquids are listed in Table 2:

General Storage and Handling Precautions:

• Keep flammables away from all ignition sources including sparks, open flames, hot surfaces, and direct sunlight.
• Store flammables separate from other hazard classes, especially oxidizers and corrosives. Use secondary containment if incompatibles must be stored in the same location.
• Separate flammable gases from oxidizing gases with an approved non-combustible partition or by a distance of 20 feet.
• Store flammable liquids in approved safety containers or cabinets.
• In instances where static electricity may accumulate and ignite flammable vapors, ground and bond flammable liquid containers.
• Keep flammable liquids that require cold storage in laboratory safe and explosion proof refrigerators and freezers to avoid ignition of the materials by sparks or static electricity. Never store flammables in a refrigerator not designed and approved for flammable storage.

Container Size Limits:

• Individual glass containers of Class I-A liquids must not exceed 1 pint (500 mL) capacity. Individual glass containers Class 1-B liquids must not exceed 1 quart (1 liter) capacity. Exception: Class I-A and I-B liquids may be stored in factory-shipped glass containers up to 1-gallon or 4-liter capacity if the required liquid purity would be affected by storage in metal containers or if the liquid would cause excessive corrosion of a metal container.
• Class I-A liquids can be stored in metal containers not larger than 1 gallon (4 liters) capacity, or U.L. listed safety cans not larger than 2 gallons (8 liters) capacity. A safety can is a listed container, having a spring-closing lid, spout cover and a flame arrester and so designed that it will safely relieve internal pressure when subjected to fire exposure.
• For liquids other than Class I-A liquids, the capacity of metal containers and safety cans must not exceed five gallons each.

Flammable Storage Limits Outside of a Cabinet:

• Limit quantities of flammable liquids stored outside of safety cans and flammable storage cabinets.
• Laboratories are allowed to store no more than 10 gallons of flammable liquids outside of a flammable cabinet.
• Laboratories are allowed a maximum of 20 gallons of flammable liquids stored in safety cans outside of a flammable cabinet.

Flammable Storage Limits Inside of a Cabinet:

The maximum quantity of Class 1A flammable liquids allowed to be stored in a flammable cabinet is 60 gallons. The maximum quantity allowed for all classes of flammable liquids is 120 gallons per cabinet.

Corrosive chemicals include strong acids and bases which can destroy human tissue and corrode metals. Acids and bases are incompatible with one another and may react with many other hazard classes. Table 3 outlines the different types of corrosives.

General Storage and Safety Precautions:

• Segregate acids from bases. Segregate inorganic oxidizing acids (e.g., nitric acid) from organic acids (e.g., acetic acid), flammables, and combustibles.
• Segregate acids from chemicals that could generate toxic gases upon contact (e.g., sodium cyanide and iron sulfide).
• Segregate acids from water reactive metals such as sodium, potassium, and magnesium.
• Always handle concentrated corrosives in a fume hood with the sash properly aligned to provide splash protection.
• Store corrosives on lower shelves, at least below eye level and in compatible secondary containers.
• Concentrated solutions must always be handled in a fume hood.
• A laboratory coat, splash goggles, and chemically resistant gloves are required when handling corrosives.
• When diluting concentrated acids and bases, always add the concentrated solution to water slowly.
• All laboratories that use Hydrofluoric acid (HF) are required to have calcium gluconate on hand in case of an exposure. Users of HF must be trained on using the gluconate.
• Chemicals must always be stored according to compatibility. Incompatible chemicals must be stored in different locations or segregated from other chemicals using secondary containment.

Additional Safety Information: 

Hydrofluoric Acid Safety Update

An oxidizer is any material that readily yields oxygen or other oxidizing gas, or that readily reacts to promote or initiate combustion of combustible materials, and under some circumstances, can undergo a vigorous self-sustained decomposition due to contamination or heat exposure.

The hazards associated with chemical oxidizers include the potential to:

1. Increase the burning rate of flammable and combustible materials.
2. Cause spontaneous ignition of flammable and combustible materials.
3. Decompose rapidly.
4. Evolve or emit hazardous gases.
5. Undergo self-sustained decomposition, which can result in an explosion.
6. React explosively if mixed with incompatible materials or if involved in a fire.

Identifying oxidizers by Chemical Name and Formula

Oxidizers have excess oxygen and can sometimes be identified by prefixes and suffixes in the chemical name. Many oxidizers contain the prefix “per” and suffix “ate”. Table 4 lists some common oxidizer functional groups:

Common Examples of Oxidizers

Liquids

• Benzoyl Peroxide
• Bleach (sodium hypochlorite)
• Bromine
• Chromic Acid
• Nitric Acid
• Perchloric Acid
• Piranha Solution (sulfuric acid and hydrogen peroxide)

Solids

• Ammonium Nitrate
• Potassium Nitrate
• Potassium Chlorate
• Sodium Nitrate

Gases

• Chlorine
• Oxygen
• Nitric Oxide

Safe Handling and Storage of Oxidizers

• Segregate oxidizers from flammables and combustibles.
• Segregate oxidizers from reducing agents (zinc, alkaline metals, formic acid).
• Segregate organic oxidizers such as benzoyl peroxide from all other oxidizers.
• Special consideration must always be given when choosing containers for storage of oxidizers for both use and waste collection. A container formerly containing a combustible or flammable material should never be used to store an oxidizer and vice versa. Doing so may result in a delayed or spontaneous explosion.
• Special pressure vented caps are available from EH&S for containers that may evolve gas such as Piranha Solution. These caps can also be used for waste containers used to store other oxidizers and may help prevent an explosion due to accidental contamination of a waste container containing an oxidizer.

Overexposure to toxic chemicals can cause injury or death. LD₅₀ is the most common way to express relative toxicity of a chemical. LD₅₀ is the amount of a chemical that is sufficient to kill 50 percent of a population of test animals usually within a certain time. It is expressed in mg/kg, or milligrams of substance per kilogram of body weight. Generally, chemicals with an oral LD₅₀ between 50-500 mg/kg are considered toxic, and chemicals with an LD₅₀ of less than 50 mg/kg are considered highly toxic.

General Safety Precautions for Toxics and Highly Toxics

• Toxic chemicals that produce fumes or dust should always be handled within a chemical fume hood.
• Maintain the lowest possible quantities of toxics in your laboratory.
• Keep containers tightly sealed to minimize exposure to personnel and contamination of other chemicals.

A carcinogen (defined as “select carcinogen” by Cal/OSHA) is a substance or agent that meets one of the following criteria:

1. It is regulated by Cal/OSHA as a carcinogen.
2. It is listed under the category, “known to be carcinogens” in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest edition); or
3. It is listed under Group 1 (“carcinogenic to humans”) by the International Agency for Research on Cancer (IARC)
4. It is listed in either Group 2A or 2B by IARC or under the category, “reasonably anticipated to be carcinogens” by NTP, and causes statistically significant tumor incidence in experimental animals in accordance with any of the following criteria:

• After inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime to dosages of less than 10 mg/m3.
• After repeated skin application of less than 300 mg/kg of body weight per week; or
• After oral dosages of less than 50 mg/kg of body weight per day.

General Safety Guidelines

Carcinogens are considered Particularly Hazardous Chemicals (PHC’s) at UCSF. Principal Investigators with carcinogens in their inventories are required to create SOP addressing the safe use of the carcinogen they are using. The following guidelines are generally applicable for experiments involving carcinogens:

• Use the smallest amount of chemical that is consistent with the requirements of the work to be performed.
• Use containment devices such as laboratory fume hoods or glove boxes when volatilizing these substances, manipulating substances that may generate aerosols, and performing laboratory procedures that may result in uncontrolled release of the substance.
• Use high efficiency particulate air (HEPA) filters, carbon filters, or scrubber systems with containment devices to protect effluent and vacuum lines, pumps, and the environment whenever feasible.
• Use ventilated containment to weigh out solid chemicals. Alternatively, the tare method can be used to prevent inhalation of the chemical. While working in a laboratory hood, the chemical is added to a pre-weighed container. The container is then sealed and can be re-weighed outside of the hood. If chemical needs to be added or removed, this manipulation is carried out in the hood. In this manner, all open chemical handling is conducted in the laboratory hood.
• Use a properly functioning lab fume hood when handling carcinogens.
• If the process does not permit the handing of such materials in a fume hood, contact your DSA for reviewing the adequacy of ventilation measures.
• In addition to proper street clothing (long pants or equivalent) that covers legs and ankles, and close-toed non-perforated shoes that completely cover the feet, wear a lab coat, appropriate eye protection and chemically resistant gloves.

More Information about Carcinogen Use at UCSF:

• Quick Guide for Principal Investigators and Lab Supervisors Carcinogen Safety Program
• Formaldehyde Use Guidelines

Pyrophoric materials are chemicals that spontaneously ignite in the presence of air, some are reactive with water vapor, and most are reactive with oxygen. Because pyrophoric substances can spontaneously ignite on contact with air and/or water, they must be handled under an inert atmosphere and in such a way that rigorously excludes air and moisture. Some pyrophoric materials are also toxic and many are dissolved or immersed in a flammable solvent.

Two common examples are organolithium reagents and white phosphorus.

General Storage Requirements for Pyrophoric Materials

• Only minimal amounts of pyrophoric chemicals should be used in experiments or stored in the laboratory.
• These chemicals must be stored as recommended by the Manufacturer’s SDS. Suitable storage locations may include inert gas-filled desiccators or glove boxes; however, some pyrophoric materials must be stored in a flammable substance approved freezer.
• If pyrophoric or water reactive reagents are received in a specially designed shipping, storage or dispensing container (such as the Aldrich Sure/Seal packaging system), ensure that the integrity of that container is maintained.
• Ensure that sufficient protective solvent, oil, kerosene, or inert gas remains in the container while pyrophoric materials are stored.

Explosive chemicals can rapidly release tremendous amounts of destructive energy and cause death, serious injury, or severe property damage. Heat, shock, friction, or even static electricity can initiate explosions of these chemicals. Explosive chemicals include the following classes of chemicals:

Nitrogen Oxides (e.g., Nitrates, Nitro)

• ethylidene dinitrate
• picric acid (dry)
• thallium aci-phenylnitromethanide
• trinitrotoluene (TNT)
• hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)
• octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)

Oxides, Peroxides, and Related Chemicals

• benzoyl peroxide (97%) (dry)
• bis (1-chloroethylthallium chloride) oxide

Nitrogen-Rich Chemicals (e.g., Azo-, Diazo, Triazo, Tetrazole)

• aluminum azide
• 5-aminotetrazole
• 1-bromoaziridine
• chromyl azide chloride
• diethyl diazomalonate
• hydrogen azide (>17%)
• lead azide
• mercury (I&II) azide
• molybdenum diazide tetrachloride
• sodium diazomethanide
• tetrazole
• 1,2,3-triazole

Perchlorate Chemicals

• ammonium perchlorate
• ethyl perchlorate (the most explosive chemical known)
• hexyl perchlorate

Acetylenic Chemicals

• n-chloro-3-aminopropyne
• propiolic acid
• 3-propynethiol
• 4-sodium hexakis(propynyl)ferrate

Potentially Explosive Chemicals

In addition to explosive chemicals, which constitute a known high hazard, there are chemicals that may become explosive, depending on how they are handled. This category is commonly referred to as potentially explosive chemicals and includes:

• Organic chemicals, such as ethers, that form peroxides through exposure to air or light
• Hydrated chemicals such as picric acid and 2,4-Dinitrophenlyhydrazine that can become shock sensitive when dry.
• Sodium amide that reacts with air or moisture.
• Certain alkyl nitrates (e.g., butyl nitrate or propyl nitrate) that become contaminated with nitrogen oxides.
• Certain normally stable perchlorates (e.g., pyridinium perchlorate or tetraethylammonium perchlorate) that becomes unstable at elevated temperatures.

Precautions for Explosive and Potentially Explosive Chemicals

• Identify all explosive and potentially explosive chemicals in your inventory.
• Always follow the safe storage guidelines outlined in the manufacturer’s SDS.
• For chemicals that may degrade to become potentially explosive, record the opening date and discard date directly onto the container.
• Keep explosive chemicals away from all ignition sources including open flames, hot surfaces, direct sunlight, and spark sources.

Overtime these chemicals can react with air to form peroxides that may explode with shock, heat, or friction. Some chemicals may also form peroxides when concentrated by evaporation or distillation. More information on the safe storage, handling and disposal of peroxide forming chemicals is available in the Managing Peroxide Forming Compounds Safety Update on the EH&S website.

General Precautions for Peroxide Forming Chemicals

• Where possible always purchase peroxide formers with an inhibitor.
• All peroxide formers must be dated with date received and the date opened.
• Peroxide formers must be tested for peroxides periodically and before distillation to ensure dangerous peroxide formation has not occurred.
• Uninhibited peroxide formers such as Tetrahydrofuran should be stored under an inert gas to prevent peroxide formation.

Gas cylinders containing compressed gases contain a lot of stored energy that can cause serious injury and property damage if the cylinder is damaged or knocked over. Additional hazards can arise from the toxicity, flammability, corrosively, or reactivity of the gas in the cylinder.

Storage Precautions for Compressed Gases

• Segregate incompatible gases as you would other incompatible chemicals.
• Limit the quantity of compressed gas cylinders on site to what will be used within a reasonable period of time.
• Store cylinders upright.
• Two chains or straps must be used to secure cylinders - one across the lower third and one across the upper third of the cylinder.
• Keep cylinders away from heat and open flames.
• Leave the valve protection cap on the cylinder unless it is in use.

More requirements and guidelines for the safe use of gas cylinders is available in the Compressed Gas Cylinder and Cryogenic Liquid Safety Update

These materials are extremely cold (-100°C to -270°C). Upon contact with cryogenic materials, living tissue can freeze and become brittle enough to shatter. Additional hazards include rapid pressure buildup, oxygen enrichment, and asphyxiation. Rapid pressure buildup could lead to an explosion if a cryogen is improperly contained. Cryogenic liquids and gases have many properties and hazardous characteristics in common with compressed gases.

General Precautions for Using Cryogens

• Store and handle in a well-ventilated area. When liquid cryogens are converted to the gaseous phase, they may create an oxygen deficiency. Do not use cryogens in small enclosed areas.
• Use only approved storage vessels (i.e., thermos-like evacuated, double-walled containers) with pressure relief mechanisms. Non-approved vessels may explode.
• Secure containers so they will not tip over or obstruct an aisle, hallway, or corridor during an earthquake.
• Liquid nitrogen and liquid helium are capable of liquefying oxygen from air. This form of oxygen enrichment can become a strong fire or explosion hazard.
• Use appropriate protective equipment for handling cryogens: insulated holders for carrying vessels; eye protection, goggles, or face shields, and cryogenic gloves.

More requirements and guidelines for the safe use of cryogens available on the Compressed Gas Cylinder and Cryogenic Liquid Safety Update