Chemical Segregation, Storage, and Incompatible Chemicals

Chemicals are an important component of laboratory functions. If used carelessly, they can cause severe physical, structural, and/or financial damage to the University and its employees.

These damages may be brought about by an immediate reaction or long-term misuse/neglect of a chemical. To prevent the misuse of chemicals, the employee must identify any hazards associated with the chemical in use. This can be done by reviewing the Safety Data Sheet (SDS) before working with the chemical. Plan work carefully. At the beginning of complex research projects, conduct a risk assessment. Ask these questions:

  • What are the hazard(s) associated with the chemicals involved in the research? (Nitric Acid, Xylene, Sodium Azide)
  • What kind of PPE is needed? (fume hood, biosafety cabinet, apron, splash-proof goggles)
  • Will the process generate waste? 
  • Will the waste be hazardous? (reactive, ignitable, corrosive, toxic) 
  • What type of reactions take place when using the chemicals? (generate heat, acid-gas formation, freeze)

Tips for Chemical Storage

Many laboratories find it convenient to store their chemicals alphabetically. This may seem like good lab organization, but it can lead to incompatible hazardous chemicals being stored together. For example, say we store all the chemicals starting with "S" together. What usually happens in this situation is Sulfuric Acid (Strong Acid) gets stored on the same shelf or in the same cabinet as Sodium Nitrite (Strong Oxidizer).  If one of these containers leaked (or the shelf falls), an acid gas could result as a reaction between the two chemicals. Consult the chemical's SDS for identifying hazards and compatibility issues. See below for tips on chemical storage. Click here‌‌ for the Chemical Segregation Tip Sheet.

  • Separate solids from liquids (preferably organic from inorganic). Note: Within the solids group, separate metals from non-metals. Keep metals away from water and moisture to prevent corrosion or reaction.
  • Separate non-hazardous from hazardous.
  • Separate toxic from irritants (non-hazardous). Note: Irritants are usually denoted by a black "X" on the bottle. Toxic are labeled with a skull-and-crossbones symbol. Toxic chemicals should be stored away from sink and sanitary areas.
  • Containers of flammable liquids are often stored in refrigerators or cold rooms. This is an unsafe practice. Evaporation occurs, and in the closed chamber, an explosive mixture may rapidly be achieved. A spark from a door switch, light mullion heater, defrost timer, compressor relay, thermostat, or other source can result in an explosion. Cold rooms also may have many ignition sources, typically from fan motors, light switches, or electrical equipment being operated in the room.

    Evaporation of flammable liquids can occur even from tightly capped containers. At lower temperatures, this happens at a slower rate, but if the chamber is opened infrequently, the concentration of vapor may still approach the lower explosive limit. Spills of flammable liquids within a refrigerator also are a major hazard. The spark from the door switch when the refrigerator opens will result in an explosion.

    If flammable materials must be refrigerated, they should be stored in explosion-proof or laboratory-safe refrigerators. These units differ greatly but are both suitable for most research laboratory applications. The sources of ignition are eliminated from the chamber (e.g., light, door switch, thermostat). These units possess a magnetic door catch instead of a mechanical latch to eliminate a source of sparks.
  • Separate corrosives from remaining hazardous chemicals including flammables. Note: Among the corrosives, separate acids from bases. Acids and bases can be stored in the same cabinet as long as they are stored in secondary containment separate from each other. Corrosives can be stored in cabinets underneath fume hoods (usually in the cabinet provided on the right). 
  • Separate reactive/oxidizers from remaining hazardous chemicals. Note: Oxidizers can be stored on shelves, preferably below eye level. Some oxidizers can be stored in explosion-proof refrigerators to prevent peroxide formation. Water-reactive chemicals should be stored clear of sinks or any areas of moisture.
  • Review the list of Chemical Substance Incompatibilities to further refine your chemical segregation.
  • The Group A and B incompatible chemicals list also can be useful for determining how to segregate your chemicals. 

If you require further assistance on how best to segregate your chemicals, contact EHS at 410-706-7055 for a consultation.

What to do with your chemicals if you are moving buildings or leaving the University

If you are leaving the University or moving to another building (or lab space), be sure to remove all unwanted chemicals from the lab before you leave the building (or lab space). The EHS Audit Team has found chemicals left behind by previous labs (some 20-plus years old) that current users are not aware of, nor have they been trained on their potential hazards. Old or expired chemicals present serious hazards for lab personnel and EHS employees who manage the disposal of these chemicals. Updated chemical inventories and frequent housekeeping will prevent the unnecessary accumulation of chemicals. EHS can provide lab chemical cleanouts if you do not want to take chemicals with you.

Unwanted, Abandoned, or Waste Chemicals

Many of the chemicals used in research laboratories fall under EPA regulations concerning hazardous waste. Once these materials are abandoned, discarded, considered used and no longer wanted, or expired, they should be submitted to EHS for disposal as hazardous waste. Please see Hazardous Material Management for pickup request forms and more information.