Housekeeping checklist

Maintaining the lab in a clean, organized state is important both for safety and for science. After all, you can’t be doing great science when you’re spending all your time looking for tools lost in piles of junk.

Here’s a checklist to help you organize your lab. Post it on the back of the door and teach every lab researcher to run down the checklist before leaving. Just a little bit of cleanup per day will eventually make the most messy lab a tidy, efficient, and safe place to do science.

Housekeeping score sheet 2022-10-11 DRK 1

Do You Have Swiss Cheese In Your Lab?

Picture source: Ben Aveling, Wikipedia, CC-BY-SA-4.0.

One of the common models of safety incidents is the Swiss Cheese Model, due to James Reason. Generally, there are multiple different layers of protection between you and exposure to a hazard, and no safety barrier is 100% protective. The model treats hazards as passing through one or more pores in these safety barriers—hence the “Swiss Cheese” name. If the holes in the layers of protection happen to line up, and a hazard challenges them, there is a safety incident.

Things to learn from the Swiss Cheese Model:

  1. No safety barrier is 100% effective.
  2. Using multiple safety barriers generally decreases the incidence of safety incidents.
  3. This is only true if the safety barriers are independent, that is, if the “holes” do not line up.

So when you look at a hazard in your lab, ask: How many independent safety barriers are protecting me? Then consider if you might need additional barriers.

If you have questions about layers of safety protection and the Swiss Cheese model, contact Dr. Daniel Kuespert, Homewood Laboratory Safety Advocate, at [email protected]. See Dr. Kuespert’s website,, for more safety information. As always, emergency response is available from Security at 410-516-7777.



Daniel R. Kuespert, PhD, CSP | Laboratory Safety Advocate (he)

Johns Hopkins University
Krieger School of Arts & Sciences/Whiting School of Engineering
Ames Hall 241, Baltimore, MD 21218
P. 410-516-5525 | E. [email protected]


Not Rocket Science: A JHU Safety Note   


A researcher working without a lab coat spilled 10 mL of a solution containing small amounts of beta-mercaptoethanol on their forearm. The researcher removed gloves and sweater, then flushed the area with water for about 20 minutes. During this time, another student looked up the Safety Data Sheet for the spilled chemical, saw the notation “Fatal in contact with skin,” and called emergency responders.  

Security contacted HSE, which determined that negative health effects were unlikely despite the chemical’s acute toxicity due to the small volume and dilute concentration of the chemical along with the short duration of the exposure.  


  • Wear appropriate PPE for the task. 
  • A laboratory coat, particularly one which is chemical-resistant, can provide substantial short-term protection from chemical splash. 
  • Gloves must be chosen for the chemicals in use, since one glove may protect against different chemicals or exposures than another. 
  • Keep sashes lowered on fume hoods to provide more protection against splashes. 
  • Review Safety Data Sheets before working with a chemical.  
  • This is university policy and is not optional! 
  • Pay particular attention to first-aid instructions. 
  • Resources for SDSs 


  • How do we ensure that all lab occupants have read the SDS of a given chemical before working with it? 
  • How might the outcome of this incident have changed had the SDS for this chemical not been consulted? 
  • How do we select and use the correct personal protective equipment? 
  • What does the role played by the other student in this incident show about the roles of buddies in the lab? 


Contact Dr. Dan Kuespert, Laboratory Safety Advocate, at 410-516-5525 or [email protected] for
more information about this JHU Safety Note. 


Lab Safety Defense-in-Depth

In this month’s Safety Short, learn about how the military concept of Defense in Depth translates to laboratory safety.

There is a very successful concept in military strategy called Defense In Depth. It refers to the use of multiple layers of defensive measures; these are usually intended to cause damage to the enemy and then be abandoned. A similar concept applies in occupational health & safety.


In safety, Defense In Depth refers to the use of multiple layers of hazard controls to minimize risk.


Any risk minimization measure one might use to protect lab workers against a hazard will be less than 100% effective. Building sprinkler systems, for example, only work when water and electricity are available, and when the system is properly maintained.

We can add layers of protection to the sprinkler by establishing an inspection and test program for it, or by providing an alternative source of water. We can also add other risk minimization measures to add layers, such as building the laboratory out of noncombustible materials.


How effective each of these layers is can be determined from the NIOSH Hierarchy of Controls, which we discussed in June 2021. In general, engineering controls are more effective than administrative controls, which are in turn more effective than personal protective equipment. The laws of probability illustrate that the probability of an incident given 2 independent layers of protection will be less than or equal to the probability of an incident given only one layer of protection. Adding more independent layers reduces the likelihood of an incident.


If you have questions about layers of safety protection, contact Dr. Daniel Kuespert, Homewood Laboratory Safety Advocate, at [email protected]. See Dr. Kuespert’s website,, for more safety information. As always, emergency response is available from Security at 410-516-7777.

In Memoriam

Someone dies in a laboratory in the United States about once a year. This is far less than the number who die in steelworking, for example, but then again, there are more steelworkers than lab workers. One can argue over who has the higher death rate. Sometimes we forget that even one fatality is not an acceptable result, getting bogged down in numbers and neglecting the fact that “the fatality” was a real person.

To help combat this tendency to focus on numbers, the Laboratory Safety Institute ( has a Memorial Wallon its website listing the name of each victim (if known), year of death, and what details are known about the person’s death. Persons on the list range from Sheri Sangi, who died from exposure to hazardous chemicals in 2009, to historical figures such as Hopkins’ own Fredrick Baetjer, a pioneer in X-ray studies, who died in 1933 of chronic overexposure to X-radiation.

If you have questions about lab safety, contact Dr. Daniel Kuespert, Homewood Laboratory Safety Advocate, at [email protected]. See Dr. Kuespert’s website,, for more safety information. As always, emergency response is available from Security at 410-516-7777.

Annual JHU Freezer Challenge

Did you know that ultra-low temperature freezers consume as much electricity annually as a typical single-family home? Lower your lab’s carbon footprint and challenge your cold storage practices by taking part in the Freezer Challenge. Supported by the International Institute for Sustainable Laboratories (I2SL) and My Green Lab, this challenge is designed to promote best practices in cold storage management for laboratories around the world.

The annual competition operates from January to July and the top JHU winners will be awarded a cash prize. In addition, the overall winner of the international challenge will be featured in Nature magazine and awarded during the annual I2SL conference.

To learn more, please register for a virtual information session next Tuesday, January 18th, from 11:00 am to noon, or fill out this participation interest form.

To learn more about our other Green Labs initiatives, please visit: or email [email protected].

STEM Graduate Student Wellness Seminar: Sleep and Mindfulness

The JHU Center for Health Education and Wellness and the Homewood Laboratory Safety Advocate are pleased to present a student wellness seminar on “Sleep and Mindfulness,” scheduled for January 25, 10:30-11:30 am on Zoom. Molly Hutchison of CHEW will be the presenter.

While these topics have direct relevance to lab safety, they apply to all students; it’s a health seminar, not a specifically “safety” seminar. Students from all STEM departments are invited to attend.

To register, use the following link:

Questions about the seminar can be directed to Dr. Daniel Kuespert, Laboratory Safety Advocate, at [email protected] or 410-516-5525

Substitutes for Mercury in Lab

Although its use is declining, some of our laboratories still use elemental mercury metal. Two places mercury is commonly found are manometers and thermometers.
Mercury is quite toxic, volatile (it evaporates into the air where you can breathe it in), and can be difficult to clean up. University policy is that mercury should be eliminated from all possible applications.

Substitutes are available for almost all uses of mercury. For example, modern thermometers offer the same or better accuracy and precision as a mercury thermometer, using an alcohol-based fluid. A manometer can be traded out for a pressure transducer whose performance is probably superior to the old manometer. (Manometers really provide accuracies of only about 2%, according to the National Institute of Standards and Technology.)

If you have mercury in your lab, whether a vial of liquid metal, an old thermometer, or a manometer for pressure measurement, please contact Health, Safety & Environment at 410-516-8798 and ask for it to be removed. If you need assistance finding a suitable replacement instrument, please contact Dr. Dan Kuespert, Laboratory Safety Advocate, at [email protected] or 410-516-5525.