Chemical Segregation Procedure

Identification of chemical hazards relies on the user to recognize and understand the labeling system used by manufacturers. All chemicals must be classified for the appropriate hazards, and stored away from incompatible chemicals. Alphabetizing chemicals is not permitted as the sole means of chemical storage.
Each group of chemicals must be stored within secondary containment capable of holding the full contents of the largest container, or at least 10% of the total volume of all containers in it (whichever is larger). Clean equipment and surfaces regularly to prevent reactions from cross-contamination.

Hazard Classification:
Chemical reagent bottles should be labeled from the manufacturer. Older or smaller bottles may not have hazards clearly marked. Consult the Safety Data Sheet (SDS) for each chemical to determine the appropriate hazard(s).
Begin by separating out inorganic chemicals from organic chemicals. Next, separate the solids from liquids for each group. The following instructions will address the most commonly used chemicals found in a University lab. Some chemicals possess two or more hazards. Refer to the appropriate SDS or contact the Department of Environmental Health and Safety (EHS) with specific questions.

Steps for Chemical Segregation:

• 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. 

A) Solids, Inorganic or Organic

1. Separate Water-reactive chemicals, Flammable Solids, and Oxidizers into groups.
2. Identify Corrosive chemicals, separating Acids from Bases.
3. Separate Toxic and Irritant chemicals from the remaining non-hazardous chemicals.

B) Liquids, Inorganic or Organic

1. Identify Corrosive chemicals, separating Acids from Bases.
   1. Within the Inorganic Acids, segregate the corrosive Oxidizers
   2. Within the Organic Acids and Organic Bases, segregate the Flammable chemicals
2. Separate Oxidizers and Organic Peroxides from the remaining chemicals.
3. Separate Flammable reagents from the remaining solvents and solutions.
4. Separate Toxic and Irritant liquids from the remaining non-hazardous chemicals.

Notes:

Air-reactive chemicals should be stored under mineral oil, or in a nitrogen environment.

Water-reactive chemicals should be stored away from sinks and liquid chemicals, or in a desiccator.

Peroxide-forming chemicals must be dated upon receipt and opening, and must be discarded through EHS within a year of receipt, or six months from opening

Irritants are usually denoted by a black "X" on the bottle.

Toxics are labeled with a skull and crossbones symbol.  Toxic chemicals should be stored away from sink and sanitary areas.

Oxidizers and Corrosives should be stored below eye-level, in secondary containment. Some Oxidizers can be stored in explosion-proof refrigerators to prevent peroxide formation.

If you have more than 10 gallons of Flammable Liquids in your lab, they must be stored in a flammable storage cabinet.  Many fume hoods have flammable and/or acid cabinets built into the lower half of the unit.