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.