Think before you reach for the bleach by Christopher Aston

The sodium hypochlorite in household bleach is a strong oxidizing agent and an effective disinfectant for known, and potentially, infectious materials used in research. However, over time, the sodium hypochlorite breaks down to salt and water, thus limiting its effectiveness. By keeping in mind a few important considerations, laboratories can ensure that their bleach provides a sufficient level of potency, when needed.

When bleach and water are mixed together, 1:10, to create a cleaning or disinfecting solution, the solution rapidly begins to lose needed disinfecting properties. Therefore, it is recommended that the solution be made fresh daily. Pre-filled spray bottles that mix at the nozzle are a convenient way of generating a 1:10 mixture for use in the lab. Storage arrangements and shelf-life are also important considerations when utilizing bleach solutions for cleaning and disinfection. Stock bleach should be stored in an opaque plastic bottle at room temperature. The rate of degradation depends on the initial hypochlorite concentration, ambient temperature and the volume remaining in the bottle. Although many do, manufacturers are not required to put an expiration date on the bottle. A good practice therefore, is to mark the bottle with the received date, and replace bleach that was received more than 6 months prior. Colorimetric test strips for hypochlorite concentration provide an easy and useful monitoring tool.  As an additional measure of surety, it is possible to determine the production date of this product from the last four digits of the serial number on the bottle. The first of these digits identifies the year of production (3=2013, 4=2014) and the other three indicate the day of the year of production (002= Jan 2nd, 364=Dec 30th). For example, E63099 = production date April 9, 2013 (the 99th day of 2013). Initial hypochlorite concentration is also an important determinant of degradation rate. The potency of commercial bleach is between 3.25 and 6.15% hypochlorite, depending on manufacturer. Some brands and specific product lines, such as Ultra CLOROX, contain higher concentrations.

Finally, remember that bleach can be corrosive on some surfaces, including steel (and skin!). Bleach residue on non-porous surfaces should be wiped off with water or 70% ethanol. Bleach should not be used in conjunction with other household cleaning products that contain ammonia; the two can react to produce several hazardous byproducts, including chlorine gas.

The EH&S Biosafety team is available to provide consultation to any laboratory on disinfection products and procedures; email

Anatomy of a Laboratory Cleanout by Nicholas Craig

At certain times it may become necessary for a laboratory to conduct a cleanout of unwanted chemicals. Whether the cleanout is in advance of a laboratory move, closure, or simply due to some chemical inventory “spring cleaning,” EH&S is available to help facilitate a seamless and efficient project. There are 3 primary phases to a laboratory chemical cleanout:

Phase 1: The laboratory contacts EH&S to indicate that a chemical cleanout is needed. Once a laboratory has contacted EH&S, a Hazardous Materials Specialist (HMS) and the lab’s assigned Research Safety Specialist (RSS) will conduct a walkthrough of the space to determine the scope of the cleanout. With particularly large cleanouts, EH&S may use a vendor to pack chemicals directly out of the laboratory. Regardless of size, after the job is scoped, the second phase of the chemical cleanout begins.

Phase 2:  The laboratory identifies which chemicals will be removed versus those that will be saved.  This step is important to ensure that only unwanted chemicals are removed from the laboratory space. In order to successfully identify the correct chemicals, a method of visually indicating which chemicals are to be removed should be devised. EH&S suggests stickers, labels, colored tape, or segregating chemicals in designated bins or on a laboratory bench or fume hood where only those chemicals destined for disposal are gathered. EH&S also suggests taking photos, or if possible, providing a full inventory of chemicals to be discarded, to help make the removal process more efficient.

Phase 3: Once all chemicals are marked and/or segregated, EH&S performs a pre-disposal walkthrough with a designated representative from the laboratory to verify which chemicals are to be removed; EH&S will photo-document the full inventory of chemicals for disposal. Once the chemicals have been removed from the laboratory space, a final walkthrough will be conducted with an HMS, RSS, and the designated representative from the laboratory in order to ensure that all of the chemicals were removed and that the lab can return to its research activities without interruption. 

page 5 Page 5

Page 1 | Page 2 | Page 3 | Page 4 | Page 5 | Page 6
Go to EH&S Home Page