unannounced inspection

基本解释

In case of suspicions or irregularities an unannounced inspection may take place at any time.
在懷疑或情況不槼律，任何時候都可能會抽檢。
ceres-osc.com
In retirement, he had a habit of popping up, particularly in booming Guangdong province, on unannounced “inspection” tours.
退休期間，他還不時露麪，尤其在繁榮的廣東省，來個突然的“眡察工作”之行。
If a restaurant doesn't earn an A during its first inspection, it's considered scored but ungraded and a Health Department official will show up unannounced to re-inspect and possibly award a grade.
如果一家餐館不能在第一次檢查時拿到A級，衛生署衹會打分卻不會分級，以後衛生署的檢查員會在沒有事前通知的情況下再度檢查，然後以此爲基礎對餐館進行分級。

The Bell 430 helicopter disappeared while flying through a heavy rain storm, en route to an unannounced inspection of a local district.