Which component is NOT critical to the construction of an IED?

The ignition safety system is not considered a critical component in the construction of an improvised explosive device (IED). The essential elements usually include a power source, an explosive main charge, and a container.

The power source provides energy for the triggering mechanism, while the explosive main charge is the material that generates the explosive reaction. The container is vital as it holds the components together, directing the force of the explosion. Although an ignition safety system can enhance the safety and effectiveness of an IED, it is not a fundamental requirement for its basic construction. Therefore, its absence does not prevent the creation of a functional IED, which is why it is the correct answer to the question.