Chapter 8: Chemical Safety

Effective Date: July 1, 1997 (Issue No. 2)

Last Updated: September, 2023

A. Introduction

The chemicals discussed in this document include elements, compounds, mixtures, commercial products, cleaning products, solvents, and lubricants. Many chemicals are poisonous, irritating, corrosive, carcinogenic, pyrophoric, or explosive. It is not uncommon for chemicals to have two or more of these properties. Chemicals that may be relatively safe when used alone can become very dangerous when mixed with other substances, either in a planned experiment or by accident. Furthermore, a material may not present any risk of exposure in one form, but may in another (e.g. solid vs. aerosol). Therefore, personnel who handle chemicals must consider the hazards and use appropriate controls and procedures.

In Hong Kong, the storage and use of dangerous chemicals are regulated by the Fire Services Department under the Dangerous Goods Ordinance. Personnel exposure to chemicals is regulated by the Labour Department while the disposal of chemical waste is regulated by the Environmental Protection Department. Violation of any of the above-cited requirements may result in criminal prosecution.

This document is intended to provide the user of chemicals with general guidelines on safe storage, and use of such chemicals in compliance with regulatory requirements. HSEO offers general chemical safety training covering good laboratory procedures, regulatory requirements, and University policies. Supervisors are responsible to ensure that their staff and/or students are properly trained. Supervisors are also responsible for providing job-specific safety training. Situation and job specific training is the responsibility of the lab supervisor.


B. Planning

The user must evaluate each task in which chemicals are used to determine the associated risk. This evaluation must include:

  • Hazardous properties of the material (explosive, flammable, toxic, etc) including target organs for toxics.
  • Routes of entry (inhalation, ingestion, skin absorption) as they relate to the experimental set-up /operation.
  • A consideration of the properties and reactivity of the chemicals or combination of chemicals.
  • Eventual disposal options and waste minimization techniques should also be evaluated in the planning stage.


Furthermore, the tasks and chemicals involved should be reviewed by a knowledgeable person in advance of the operation. All laboratory operations involving hazardous chemicals should have a written work plan prepared in advance which addresses the hazards as well as their controls. Controls include in their order of priority:

  • Engineering aspects such as the use of fume cupboards or substitutions using less hazardous materials, Administrative aspects such as work plans, operational safety procedures (OSP - see sample in Chapter 2 Work Planning & Procedures Appendix 2B), job specific training, etc. Personal protective equipment (PPE) such as safety glasses (required in all labs), chemical splash goggles, chemical resistant gloves, respirators, etc.


C. Responsibilities

Principal investigators/supervisors are responsible for establishing safe procedures and providing the protective equipment needed in handling chemicals. They must instruct their personnel as to the possible hazards, the safety precautions, waste handling, the consequences of an accident, and the actions to take in case of an accident. It is also his/her responsibility to assure that employees and students are held accountable for the chemicals they work with. In case of a job/program transfer or termination, employees or students must properly dispose of or transfer all chemicals to another responsible party before leaving.

Employees and students are required to learn and understand the properties of the chemicals they work with and to follow all precautions applicable to each task. In case of unexpected malfunctioning, damage, or injury occurs, the employee and student should take prompt action to protect himself and others in the area. He or she should also report to the supervisor any unsafe or hazardous condition in the area.

The Health, Safety and Environment Office (HSEO) assists supervisors, employees and students in maintaining safe work areas by providing information on the hazardous properties of materials, recommending methods for controlling them, and for monitoring the work environment. In addition, the HSEO offers formal education and general training courses on the recognition, evaluation and control of various safety hazards.


D. Material Safety Data Sheets

Some countries require chemical manufacturers to prepare Safety Data Sheets (SDSs) for their customers. Each data sheet provides detailed information on the physical, chemical, and physiological properties of a particular chemical and on recommended control procedures to be used during handling. These data sheets are available through the Library on-line CD network as well as from CLS, Center for Laboratory Supplies.

If SDSs are not available from either of these sources, or if the manufacturer’s SDS lacks information needed for safe use of the material, the supervisor should request assistance from HSEO.


E. Facilities and Equipment

Adequate facilities and the equipment necessary to control the hazards related to specific chemical operations must be obtained before work is started. General requirements for areas using chemicals include the following:

  • secure cabinets and shelving used for chemical storage.
  • an approved type emergency safety shower and eyewash station.
  • local exhaust ventilation, fume hoods, or close-capture systems for any experiment that produces hazardous quantities of gas, vapour, or airborne particulates in the work environment. Such ventilation must be the once-through type that permits no recirculation of exhaust air.
  • floors and bench-top surfaces with impermeable films for easy cleanup of spilled materials.
  • appropriate face shields, safety goggles, liquid-proof aprons, and gloves for handling corrosive chemicals.
  • separate containers for disposal of uncontaminated broken glass.
  • an appropriate waste container for disposal of used hypodermic syringes.
  • an appropriate waste container for disposal of broken mercury containing thermometers separate from the broken glass or sharps containers.
  • Emergency ventilation (EV) system in rooms with fume hoods or close-capture systems for any experiment that produces hazardous quantities of gas, vapour, or airborne particulates in the work environment.


You may contact FMO-LS about fume hoods, local exhaust ventilation, EV and laboratory furniture. CLS can help with personal protective equipment such as gloves, face shields and special laboratory waste containers.


F. Purchase of Chemicals

  • Before acquiring toxic or hazardous chemicals, ensure that the material is the least toxic or hazardous material available which will still accomplish the research or experimental objectives (i.e. whenever possible substitute a less toxic or hazardous material in place of a more toxic or hazardous material).
  • When you check the appropriate box for chemical purchase on the Budget Requisition (BR) form, the document will be routed through HSEO for screening. HSEO staff will provide suggestions of less hazardous alternatives and/or ensure suitable measures are in place for safe handling and usage of the chemical to be purchased.
  • Before proceeding with purchase of chemicals, check the Chemical Exchange Program webpage to see if the chemicals are available for free through CEP. This is a service provided by HSEO to minimize wastage of usable reagent grade chemicals.
  • When acquiring toxic or hazardous chemicals, obtain the smallest quantity required for your work which will be consumed prior to expiry date if there is one.
  • Purchase chemicals in shatter-proof containers whenever possible.
  • Ensure that any import or storage licensing requirements have been met. CLS will be able to help.


G. Chemical Storage

Bulk quantities of dangerous goods (DG) should be stored in DG Stores according to requirements stated in the DG licenses issued by the Fire Services Department. The central DG stores on campus are under the control of CLS.

You should contact them BEFORE you acquire bulk quantities of hazardous chemicals.

General requirements for keeping small quantities of chemicals in laboratories are as follows:

  • Clearly label the storage area and each container. Container labels must give the generic chemical name, type of hazard, special precautions, and emergency information.
  • Store heavier items on lower shelves, but not on the floor.
  • Chemicals, particularly those known to decompose with time, should also be marked with the date of receipt. All containers of peroxide forming chemicals are to be labeled with receipt and opened dates and are to be monitored for the formation of peroxides (see Section I below).
  • Carcinogens and highly toxic chemicals should be stored in double containment. It is recommended that inventories of confirmed human carcinogens be maintained and that these materials should be stored in locked cabinets to ensure proper management of stock.
  • Separate incompatible chemicals by physical barriers. See Appendix 8B for examples or contact HSEO for information on specific chemicals.
  • Provide a means to contain spills of liquid chemical, i.e. secondary containment (e.g., trays).
  • Limit quantities and observe shelf-life limits.
  • An explosion-proof refrigerator is needed to store flammable chemicals that tend to decompose at room temperature.


Although the current DG Ordinances and Regulations do not contain specific legislation on chemical storage in laboratories, a set of guidelines have been developed by the FSD. Laboratory users should cooperate with HSEO to ensure compliance with these guidelines, which may include measures such as removing excessive amount of chemicals to DG stores, reducing chemical stocks in individual laboratories, and observing maximum storage quantities within a single fire compartment of the building, which usually consists of multiple laboratories.


H. Handling Solid and Liquid Chemicals

The number of chemicals and their hazardous properties and reactions are so extensive that even chemists are still discovering new properties and reactions. Therefore, if the properties of a chemical are not fully known, it should be considered hazardous. Each laboratory should establish a written chemical hygiene plan, but as a minimum the following safety procedures should be observed when working with chemicals:

  • Keep the work area clean and orderly.
  • Do not eat, drink, smoke, apply cosmetics, or store food in the work area.
  • Read all container labels and SDSs for safety information as a minimum.
  • Use required safety equipment. The minimum protective clothing is a laboratory coat and safety glasses. For additional protection, wear chemical-resistant gloves and a face shield.
  • Isolate hazardous operations in separate rooms; limit the number of personnel involved.
  • Whenever possible, select chemicals that are the least hazardous.
  • Use mechanical aids for all pipetting procedures, i.e. never mouth pipette.
  • Limit the volume of volatile or flammable materials to the minimum required for short operations.
  • Provide a means for containing the material if equipment or containers break or spill their contents.
  • Provide safe, conveniently located sinks and hand cleaners. (Do not use organic solvents for washing hands or skin.)
  • If the operating system is used under pressure or can generate pressure, follow the requirements in pressure safety program.
  • When transporting chemicals from one area to another, place the chemical bottle into a plastic bucket as a secondary container to contain spillage in case of breakage.
  • Work inside a fume hood when handling or using chemicals that are volatile, toxic or highly reactive, following appropriate fume hood usage requirements. Use suitable local exhaust ventilation when using chemicals in processes that cannot be accommodated in a fume hood.
  • Work inside a glove box with an inert atmosphere when handling or using chemicals that are air-sensitive.


I. Peroxidizable Materials

Peroxidizable materials, when in the presence of oxygen and stored for long periods of time, or when exposed to sunlight, form unstable peroxides. These peroxides may explode if the container is shaken or heated. Examples of peroxidizable materials are ethers, alkali metals, olefins, and vinyl monomers. The most hazardous ones are isopropyl ether, di-vinyl acetylene, vinylidene chloride, potassium metal, and sodium amide. Contact HSEO for more information.

All peroxidizable materials must be labelled. These types of materials which are obtained through the central store are delivered to the labs with the labels affixed. If laboratories make direct purchases of these types of materials, it is the responsibility of the lab supervisor that this stock is properly labelled. The labels can be downloaded at the HSEO website. The person opening a new container must include the date opened on the label and store the material in a cool, dark, and well-ventilated area. The container and its contents must be discarded as hazardous waste after 3 months to 1 year from the date of opening, or from the date that inhibitor was added and tests showed no peroxide formation. Caution: opening old containers of peroxidizable materials can disturb peroxides formed in the lid and cause explosions. After opening peroxidizable materials, it is safer to discard leftover materials as hazardous waste than to store them.


J. Handling Gases

Use considerable care when handling gases. When released into the work environment, gases can be inhaled or come in contact with unprotected human tissue. Employees or students who work with gases should be familiar with their properties and their reaction with the human body. In addition, some gases are corrosive, flammable, explosive, or radioactive. The following few examples illustrate these points.

  • Acetylene is incompatible with silver, mercury, or copper and, under certain conditions, may react explosively with any of them.
  • Nickel carbonyl is very toxic, even at low concentration.
  • In low concentration, chlorine is corrosive to metals as well as to human tissue.
  • High concentration of inert gases in the air we breathe can cause asphyxiation by displacing oxygen.
  • Some gases such as silane and phosphine may burn spontaneously on contact with air (i.e. pyrophoric). A potentially more hazardous situation can occur if the gas does not burn and an explosive concentration is allowed to build up.
  • Some gases such as phosgene are highly toxic even at low concentrations. Arsine is a gas which is toxic and is a confirmed human carcinogen.


Furthermore, since gases are usually supplied in cylinders under pressure, employees/students should be familiar with the pressure safety program (Chapter 5 Section 7).


K. Precautions for Cryogenic Gases

  • Avoid contact, both the liquid and the gases can cause frostbite. Do not touch uninsulated piping.
  • Wear loose-fitting thermal gloves, goggles and/or face shield, closed shoes.
  • Work in a well ventilated area. Liquified gas can rapidly expand when changing from the liquid to the gaseous phase, e.g. nitrogen expands almost 700-fold.
  • Never attempt to prevent vapours from escaping from cylinders of liquified, cryogenic gases. Since they are not at thermal equilibrium, vapour is produced as the liquid boils and, if not vented to the atmosphere, could produce excessive pressures and cause an explosion.
  • Use only the special (usually metal) tubing designed for use with these gases. Do not improvise with plastic or rubber tubing.
  • Be aware that oxygen enrichment and a fire hazard can result from the condensation of oxygen (boiling point -183°C) from the air onto piping cooled by liquid nitrogen (boiling point -196°C).
  • If skin contacts liquified cryogenic gases, thaw burned area slowly in cold water. Do not rub.


L. Disposal

Waste chemicals and spent chemical solutions produced by experiments can have hazardous properties and pose a threat of contamination to the environment. During the planning stage, every effort should be made to scale the experiment in such a way as to accomplish the objective, while minimizing the amount of hazardous waste generated.

Hazardous waste items must be collected either in a retention tank system or in specific containers provided by Enviropace for disposal by HSEO. Contact HSEO for information on proper packaging, labelling, storage and proper disposal procedure of hazardous waste. Any disposal plan should be referred to Chapter 16 on Disposal of Hazardous Materials and Items under Regulatory Control in the HKUST Safety Manual to ensure compliance with University and Hong Kong Government rules and regulations.

Before disposal of unused or unopened reagent chemicals, every effort should be made to find alternative usage of the chemicals. The Chemical Exchange Program (CEP) managed by HSEO is an on-line scheme to facilitate exchange of reagent chemicals free of charge. You may visit the CEP webpage for more details.


M. Chemical Spills

Small spills (generally less than 100 ml) can usually be cleaned up safely by the employees involved. The hazardous properties of the material must be considered when deciding whether it is a “small” spill or not, and therefore whether unassisted clean-up should be attempted. Employees must be trained in advance to handle cleanup of even small spills. Materials for cleanup of common chemical (small scale) spills are available from CLS. Report all spills of hazardous chemicals to HSEO.

If the spill is too large to clean up safely or if employees have been injured or contaminated, immediately call the Security Control Centre (8999). See Appendix 8A for the emergency response on chemical spill.