Campus Consortium for Environmental Excellence

Chemical Safety Levels

Project XL
Final Rule

2001 Progress
2002 Progress

Final Project Agreement
Final Agreement
XL Stakeholders
Leighton Letter
Regulatory Relief
XL Rule

Legal Aspects
RCRA and Labs
LSEM RCRA interp
Minimizing Costs
Current Reg Arena
UConn RCRA Workshop
Yale RCRA Inspection
Development of a Laboratory EMP
Glassware Waste Project
Waste Min Project
Contacts and Info
LabWAM Priorities and Accomplishments
Background Information

Fixing RCRA (Powerpoint)
Chemical Safety Levels
Kids in Labs (Powerpoint)

Region 1
Region 2

Region 3
The R&D NESHAP Development Process
Clean Air Act

Pilot Schools' Draft EMP's

EPA Midterm Report

Boston College
BC Plan
BC Standards
UMASS Boston
Environmental Management Standard
University of Vermont
Lab Workers' FAQ's
The Rule, UVM docs
Baseline Report
Informatics Green Bridge Websites LabXL Home






Chemical Safety Levels:
A Proposed System for Classifying
Chemical Safety Practices
in Microbiological and Biomedical Laboratories

and Pamela Serra
Office of Health and Safety
Centers for Disease Control and Prevention
1600 Clifton Road Atlanta GA 30333

Related pages:
Chemical Safety Levels Table Requirements for all Chemical Work CSL 2 Requirements CSL 3 Requirements CSL 4 Requirements


Microbiological and biomedical laboratories handle chemicals of varying hazards in widely varying manners and quantities. While there are biosafety levels which classify laboratories by the hazard of the biological agent and its use, there are no similar guidelines for classifying chemical safety practices. We propose a system for using chemical safety levels (CSLs) in these laboratories.

These CSLs - CSL1, Low Risk; CSL2, Moderate Risk; CSL3, Substantial Risk; CSL4, High Risk; - are classified by the chemical hazards and the nature of the work with these chemicals in the laboratory. Risk at each CSL is governed by limiting or restricting chemical usage or type of work. Standard and CSL-specific safe practices, equipment, and facilities requirements are proposed.

This work is presented as a starting basis for a CSL system, and additional details and modifications are to be worked out through a pilot project.


Microbiological and biomedical laboratories handle chemicals of varying hazards in widely varying manners and quantities. The result of this diversity is that the risk of chemical exposure is often difficult to assess and the safety requirements are not clearly defined. This is particularly true in microbiological and biomedical laboratories where scientists and laboratorians are often trained primarily in the biological sciences, focus on biological safety, and may not have strong backgrounds in the hazards of chemicals and chemical safety.

There are specific biosafety guidelines for microbiological and biomedical laboratories for handling bacterial, viral, and other microbial agents of varying hazard. These guidelines are described in terms of biosafety levels (BSLs) in the Biosafety in Microbiological and Biomedical Laboratories (BMBL) booklet provided by the Centers for Disease Control and Prevention and the National Institutes of Health. The advantage of the guidelines for these laboratories is that the agent and its use determines the risk, and the BSL defines the minimum level of protection required for worker protection in the use of that agent. This definition helps the researcher, the laboratorian, the supervisor, the manager, and health and safety personnel more clearly identify the features of the facilities, and the practices required by the BSL to protect the laboratory worker from exposure to biohazardous agents.

There are no similar guidelines which classify these laboratories using chemicals according to their relative risk or hazard. A classification system that defines chemical safety levels or CSLs would need to define a similar minimum level of worker protection in each laboratory handling hazardous chemicals. In the CRC Handbook Of Laboratory Safety, Dr. Keith Furr described a laboratory classification for chemical work and some of his ideas have served as a genesis for the chemical safety levels proposed in this paper. In our system the CSL would be based upon the risk of chemical exposure and potential hazard of the chemical. The CSL, like the BSL, would provide increasing degrees of protection by limiting the types and quantities of chemicals at lower levels, and by incorporating facility requirements, procedural requirements, and training requirements for each CSL. The CSL - CSL1 through CSL4 - parallel the biosafety levels - BSL1 through BSL4 - described in the BMBL.

The CSL assigned to a laboratory will depend upon the risks associated with chemicals being used. These risks include 1) the hazards of each chemical - for instance, flammability, reactivity, toxicity, and reported health effects; 2) the quantity of the chemical being used; and 3) the procedures in which the chemical will be used. The four CSLs will be determined by the degree of risk from hazardous chemical exposure: low risk [CSL1], moderate risk [CSL2], substantial risk [CSL3], and high risk [CSL4].

Each level of risk will be addressed separately providing sections that describe the chemicals allowed, standard and special safety practices, standard and special safety equipment, and standard and special laboratory facility requirements. The appropriate chemical safety level will be posted immediately outside each laboratory, allowing other laboratorians, facility support workers, and health and safety personnel to know what degree of protection is required in that laboratory. By assigning a CSL to each lab, the worker should know upon entering the lab what kind of chemical hazards are likely to be present and better know what precautions should be exercised in emergency situations. Laboratorians must be trained and knowledgeable of the four different safety levels to benefit from this classification. It is the responsibility of the employer to ensure all laboratorians are trained and knowledgeable about the risks from chemicals while working in the laboratory.

Designation of Chemical Safety Levels

The selection of a CSL for each laboratory shall be made by a safety professional in the Environmental, Health, and Safety Office (EHS) and after consultation with the laboratory supervisor. This selection shall be based upon the following information about each laboratory: 1) the nature of the work and the risk of exposure to hazardous chemicals during laboratory operations including the quantities being used and stored in the laboratory, and 2) the specific toxicity or hazard of the chemicals being used. The purpose of the classification is to provide information about the relative hazard from chemicals in that laboratory for persons, who may need to enter or know about the nature of the chemical work in a laboratory. The classification is divided into four hazard levels.

Specifications for Chemical Safety Level Activities

Note: the requirements for each CSL can be viewed by following the link in the table.

Chemical Safety Level Chemicals Use Qunatities Allowed Typical Operations Exposure Risk
CSL1 Laboratories - Low Risk HIGHLY RESTRICTED.
Only low hazard chemicals may be used openly. High hazard chemicals - volatile, toxic, flammable, explosive, reactive, corrosive or other high hazard chemicals - may be used only in sealed vials in small quantities.
Low hazard chemicals may be used as needed. No volatile, toxic, flammable, explosive, reactive, corrosive, or other high hazard chemicals are used except in small sealed vials, usually containing 1 mL or less of solution. Hazardous chemicals not used openly in the laboratory. May use small vials that are most often sealed with septum tops or screw caps for access by syringe or pipette. Typically instrumental laboratories may fit into the CSL1 category. Virtually no risk for exposure.
CSL2 Laboratories - Moderate Risk LIMITED.
Low hazard chemicals may be used openly and stored in needed quantities. Corrosives and NFPA 3 flammables are limited in quantities used and stored in each laboratory.

Chemicals in the restricted hazard classes listed Table 1 are not permitted in CSL2 laboratories except by special exemption by EHS. Requests for special exemption will be reviewed in light of the ability of the laboratory to use the chemical safely. Special exemptions will describe the conditions of use and storage, and the allowable quantities of these restricted chemicals. Examples of chemicals in each restricted class are shown in Table 2.

Low hazard chemicals may be used in quantities needed. Corrosive and NFPA 3 rated chemicals are not available in quantities greater than 1 liter (liquids) or 1 pound (solids).

Examples of corrosives and NFPA 3 chemicals are shown in Table 3. Chemicals in the restricted classes are not permitted except by special exemption which will specify quantities allowed.

Use hazardous chemicals, but in such a way as to minimize quantities being used and stored. Typically work with biological agents and in that work occasionally use hazardous chemicals in small quantities. Moderate risk for exposure, but limited due to restrictions in types and quantities of chemicals.
CSL3 Laboratories - Substantial Risk Chemicals of high hazard may be used but there may be restrictions in operations involving potential exposure to highly hazardous materials, such as in the synthesis or isolation of highly toxic chemicals or the use of large quantities of highly hazardous chemicals.

Work with chemicals in the restricted hazard classes listed in Table 1 are to be reported (exemption not required) and quantities of these compounds should be limited to amounts required.

Quantities are generally limited only by the need. Frequently use and store large quantities of these hazardous chemicals (>4 liter or 1 gallon bottles).

While chemicals on the restricted list may be used in needed quantities, their hazards should dictate that they be used and stored in minimum quantities required.

A large variety of chemicals of varying hazard are used in varying amounts. These laboratories are most often regarded as chemical laboratories. EHS may review operations with highly hazardous materials and make recommendations for improving operations. Substantial risk, due to use of many hazardous materials, often used in large quantities.
CSL4 Laboratories - High Risk UNLIMITED.
Use of all chemicals, including highly hazardous chemicals, is unlimited and governed only by prescribed protocols which dictate safe handling and storage procedures.
Limited only to the need. Highly hazardous chemicals should be limited to the quantities required. Special purpose laboratory where there is a significant risk for exposure to highly hazardous chemicals. Operations may involve production or isolation of these highly hazardous chemicals, and contamination of equipment and facilities is likely to occur. High due to handling of highly hazardous chemicals and likely contamination during operations.


The proposed system for classifying chemical safety practices in microbiological and biomedical laboratories is presented as a starting point for developing chemical safety levels. Many details must yet be worked out and there will be laboratories that seem not to fit in any category. Yet this paper seeks to promote a discussion for further refinements and clearer delineations of these CSLs. It is the fervent hope that this system will be viewed as a positive improvement in chemical safety practices for microbiological and biomedical laboratories since there appears to be a need for such a system. The designation of a CSL provides personnel who have a need to enter the laboratory with a means to better understand the relative risk of chemical hazard in the laboratory under normal and emergency conditions.

The recent problems with pfiesteria piscicida are also illustrative of the need for such a system. When the reports of laboratory workers becoming ill from exposure to the pfiesteria were made public, there were a large number inquiries as to what biosafety level should be used. Pfiesteria however is not an infectious disease but rather a organism which produces toxic products which likely cause the observed illness. Perhaps that work with pfiesteria should have been performed using a CSL3 classification rather than the BSL2 or BSL3 that were recommended.

The standard classification of laboratories via CSLs can be used in conjunction with other classifications, such as BSLs, radiation use, laser use, etc, to provide an overall assessment of each laboratory. This could be very useful in a laboratory registration system which could be used to give a laboratory an overall rating (Dr. Henry Mathews, CDC, personal communication). The rating can be used as a measure for justification of the need for further refinements in the laboratory. Safety professionals are continually trying find ways to make our workplaces safer. CSLs offer an opportunity to improve chemical safety in microbiological and biomedical laboratories by providing a clearer foundation upon which to build a better ethic for handling chemicals in these laboratories. Limiting of chemical usage and storage in these laboratories not only reduces the risk of chemical exposure but reduces the overall use of chemicals by these laboratories, better enabling environmental guidelines on hazardous waste reduction to be met.

The author solicits comments and suggestions that could make this system a practical and useful tool for health and safety professionals. This system will be piloted in the laboratories at the Centers for Disease Control and Prevention in Atlanta. Success at that level will allow it to be expanded to a broader audience.


The authors wished to thank Dr. Jonathan Richmond for his support and encouragement in developing this work. We also gratefully thank those in the Office of Health and Safety who provided suggestions and helpful criticisms - Dr. David Taylor, Ms. Rebecca West, Dr. Henry Mathews, Ms. Cheryl Connell, Dr. Peg Tipple, Mr. Mark Hemphill, and Ms. Jean Gaunce. Their comments have made this an improved effort.


ANSI/AIHA, American National Standard for Laboratory Ventilation, ANSI/AIHA Z9.5-1992, American Industrial Hygiene Association, Fairfax, VA (1992).

ANSI, American National Standard for Emergency Shower and Eyewash Equipment, ANSI Z358.1-1990, American National Standards Institute, NY (1990).

ASHRAE, Method of Testing Performance of Laboratory Fume Hoods (ANSI/ASHRAE 110-1995), American Society of Heating, Refrigerating, and Air- Conditioning Engineers, Atlanta, GA (1995).

Bretherick L, Hazards in the Chemical Laboratory, 4th Edition, The Royal Society of Chemistry, London, UK (1986).

CDC/NIH, Biosafety in Microbiological and Biomedical Laboratories, 3rd Edition, HHS Publication No. (CDC) 93-8395, JY Richmond and RW McKinney (eds.), U.S. Government Printing Office, Washington, DC (1993).

CDC/NIH, Primary Containment for Biohazards: Selection, Installation, and Use of Biological Safety Cabinets, JY Richmond and RW McKinney (eds.), U.S. Government Printing Office, Washington, DC (1995).

Furr AH, CRC Handbook of Laboratory Safety, 3rd Edition, CRC Press, Boca Raton, FL, pp. 76-90 (1990).

Myers GL, Liddle JA, Hill RH Jr, Needham LL. A Laboratory for Handling Chemical Toxicants Safely. Am. Ind. Hyg. Assoc. J. 48 524-527 (1987).

National Research Council, Prudent Practices in the Laboratory: Handling and Disposal of Chemicals, National Academy Press, Washington, DC (1995).

NFPA, NFPA 45 Standard on Fire Protection for Laboratories Using Chemicals, 1996 Edition,

National Fire Protection Association, Quincy, MA (1996).

OSHA, §1910.106, Flammable and combustible liquids. 29 Code of Federal Regulations, Government Institutes, Rockville, MD (1996).

OSHA, §1910.1450, Occupational exposure to hazardous chemicals in laboratories. 29 Code of Federal Regulations, Government Institutes, Rockville, MD (1996).

Ottoboni MA, The Dose Makes the Poison: A Plain-Language Guide to Toxicology, Vincente Books, Berkeley, CA (1984).