Which of the following is a criterion for a sharps container?

A sharps container must meet specific criteria to ensure safety and efficacy in handling sharp instruments like needles and blades. The requirement that it be leakproof and puncture resistant is critical because sharps can pose significant risks to both healthcare workers and patients. A leakproof design prevents any fluids from escaping, which can help to reduce the risk of contamination or exposure to potentially infectious materials. Puncture resistance is also essential to ensure that the container withstands the sharp edges of inserted items without allowing them to penetrate through the container's walls, further protecting personnel handling the container.

In the context of the other options, while transparency and washability, color-coding for hazards, and stackability and collapsibility might be relevant considerations for various types of waste containers, they do not directly address the primary safety and containment aspects essential for a sharps container. The focus on preventing leaks and punctures is paramount, as these features directly relate to the safe disposal and handling of hazardous materials.