Improper products mixing can lead to accident. Where it is possible to mix products, it is essential to have reactivity chemical matrix in order to apply robust safeguards to avoid accident.
Accidents due to inadvertent mixing of reactive chemicals have already occurred. The Chemical Safety Board launched today a case study and a video which addresses an accident occurred at October 21, 2016. Because of a mixture between sulfuric acid and sodium hypochlorite it was released a large amount of a cloud of chlorine causing impact onsite and offsite.
The case study points out the human factors that can contribute to enhance the probability of human error. The accident occurred during a sulfuric acid unloading, where the truck driver connected the acid in the sodium hypochlorite line by a connection hose.
This is a typical unintentional human error called slip that arises from a right intention, however the human makes the wrong action. This kind of error is enhanced due to human factors such as: proximity of equipment, lack of warnings, lack of inherently safer systems like different connections for reactive products (the principle of Poka-Yoke).
For existing facilities or new projects, the best way to lessen the possibility of human error is applying the Human Hazop. It is a methodology of analysis that has the aim to identify the various types of human factors and proposes recommendations to correct the deviations found.
See below the video from Chemical Safety Board (CSB).