Patients and their families have been informed of the action – which South Tyneside and Sunderland NHS Trust says is a routine training day – via social media.
Such exercises are carried out regularly onsite, a Trust spokeswoman told the Echo, as part of staff training.
In a post on its Facebook page, South Tyneside and Sunderland NHS Trust confirmed the work would take place on Wednesday.
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A statement said: “If you're attending Sunderland Hospital today [Wednesday, February 26], you might spot our ED [emergency department] teams undertaking routine training with our decontamination tent next to the Niall Quinn Centre.
“This is a training exercise that we do regularly as part of incident planning.”