It must be used carefully to avoid contamination with room air when injected.

"What precautions do you take to avoid contamination during your analysis of the evidence?"

Even in the case of these moons some caution may be needed to avoid contamination.

Holding them gingerly, to avoid contamination with his scent, George walked back through the kitchen and out into the night air.

At all stages, great care is needed to avoid contamination with colored materials.

Care must be taken to cover the dish during the long soaking to avoid contamination.

It is not enough to close our eyes in the hope of avoiding contamination by the problems.

A ship must control its environment and avoid contamination.

Brian stood staring at him, holding his hands in the air to avoid contamination.

Instead, first put them inside an acid-free box to avoid contamination.