Organic solvents are notably the most hazardous chemicals used in most laboratories. For example, there are the highly flammable and volatile alcohols, esters, ethers, and ketones, as well as the potentially toxic aldehydes, aromatic hydrocarbons, and chlorinated solvents. They are routinely used for a variety of applications due to their capability of dissolving or dispersing other substances.
Their potential for exposure and health impacts is determined by their molecular structure. With hundreds of solvents in common use, the health hazards run the gamut from carcinogenic to flammable, reproductive, and toxic effects. Similarly, exposure routes can include inhalation, dermal or skin contact, and ingestion.
The first step in working safely with these materials is to have a robust and comprehensive hazard communication program (HCP). OSHA’s standard for this is 29CFR1910.1200.1 The purpose of the standard and your program is to ensure that the hazards of all chemicals used, stored, and handled are properly classified and that the information is conveyed to employees.
The first and most critical component of the HCP is to build a chemical inventory. Every individual laboratory, storage, and use area should have a complete inventory or list of chemicals with associated important information such as material owner, date acquired, amount on hand, storage location, and accompanying safety data sheet (SDS).
Safety data sheets are the second critical component of a good HCP. The SDS contains 16 specific sections detailing information on the chemical’s constituents, physical properties, health hazards, first aid measures, personal protective equipment, and special handling and disposal requirements, among other things.2 The SDS contains all the information needed to develop your HCP, and they are critical if an exposure or incident occurs. Ensure access to the SDS is available within a few minutes at all times (i.e., 24/7).
After building your inventory of hazardous chemicals and collecting all the SDSs, you should move to the communication part of the program. This entails communicating important critical information to your employees. In other words, training your workers on the hazards of each chemical they could conceivably use in performing their job duties.
In addition to the hazards, employees should be well versed in and understand the potential exposure routes, signs, and symptoms of exposure and chemical warning properties (or lack thereof). Training should also include any personal protective equipment necessary for using the chemical as well as incident response, mitigation steps, and first aid measures.
Since we are firm believers in preventive and proactive health and safety, here are a few words on the timing of training. All employees should receive training prior to beginning any work with hazardous chemicals. Annual refresher training is an excellent tool and highly recommended. And, after any close call or incident, conduct a thorough review and retraining as needed.
Industrial hygienists are trained to anticipate, recognize, evaluate, and control all potential health and safety hazards in the workplace. Knowing that many chemical solvents pose significant risk for exposure and health consequences, we must acknowledge that exposure assessments are sometimes needed.
Many solvents have poor or no warning properties. The odor threshold could be very high or nonexistent. Other chemicals are sensitizers, meaning you initially can detect their presence but quickly get used to it. This means your workers could be exposed without knowing so.
Also, many solvents have very low permissible exposure limits (PELs). These are regulatory limits set by OSHA standards that indicate how much chemical a worker could be exposed to over an eight-hour day, 40-hour work week, and normal lifetime without adverse effects. Formaldehyde (0.75 ppm), benzene (1 ppm), and methylene chloride (25 ppm) are examples of solvents with low PELs due to their serious and toxic health effects.
It is paramount to conduct exposure assessments should any of these solvents be used regularly. Ensure workers handling the materials as well as those in close proximity are included in the assessment.
Flammable and combustible substances
According to Prudent Practices, the most common hazard in the typical research lab is a fire due to flammable liquid or the vapor produced by one.3 And the most frequent laboratory violation we hand out deals with use and storage of flammable liquids.
The National Fire Protection Association’s (NFPA) Code for Flammable and Combustible Liquids, NFPA 30, is an excellent resource and introduction to the hazards of these materials.4 NFPA 30 classifies flammables as Class I and divides them into Class IA, IB, and IC, while combustible materials are classified as Class II, Class IIIA, and Class IIIB, all based on flash points and boiling points. NFPA 30 also rates the fire hazard of flammable and combustible materials on a scale of 0 to 4 based on flash point.
The issue we cite most frequently is having excessive flammable solvents in the lab. NFPA 45, Fire Protection for Laboratories Using Chemicals, is the reference we turn to because it provides universal guidelines for safe storage.5 Chapter 4 of NFPA 45 classifies laboratories into four fire hazard categories based on the amount of flammable and combustible material in the lab. These are Class A (high fire hazard), Class B (moderate), Class C (low), and Class D (minimal). Examples of Class D are high school educational laboratories, whereas college-level undergraduate labs are usually limited to Class C.
Class A labs are allowed up to 10 gallons (38 L) of Class I flammable liquid per 100 square feet or 20 gallons (76 L) total of Class I, II, and III flammable and combustible liquid combined. These quantities can be doubled to 20 gallons of class I liquid and 40 gallons (150 L) of class I, II, and III liquids combined with the use of safety cans or storage cabinets.
In closing, here are some general guidelines for safe flammable and combustible storage:
- Do substitute nonflammable materials whenever possible.
- Do post the work area with appropriate signs (e.g., “No Smoking” and “No Open Flames”).
- Do store flammable liquids in approved storage cabinets, explosion-proof refrigerators, and safety cans.
- Do clear the area of all ignition sources.
- Do transfer flammable liquids with extreme caution.
- Do not store large, heavy containers of liquids on high shelves or in high cabinets. A good rule is to store them at shoulder level or below.
- Do not store bottles on the floor unless they are in some type of secondary containment.
- Do not store flammable or combustible solvents near heat sources or in direct sunlight.