What Must Be Labeled
The OSHA Hazard Communication Standard requires that ALL hazardous materials be labeled. Labels must appear either on the container itself, the batch ticket, placard, or the process sheets. Batch labels can be used to label all containers in a rack or cabinet, as long as it's clear what containers the label applies to.
Process sheets may also be used. This would take the form of a sample sheet or checklist for each tube in a sample rack that indicates that chemicals that are currently present in the tube. The sheets should indicate all of the information that would be required on a label.
Hazardous chemicals in portable containers which are for the immediate use of the employee who performs the transfer is the exception to this rule. These containers do not have to be labeled unless they are still present at the end of the employee's shift.