In an (ICU) at 400-bed community hospital, the head of department was quoted as saying 'We need to replace ventilator circuits for incubated patients on a daily basis because we thought this helped in preventing pneumonia, but evidence shows that the more we interfered with the device, the more often we risk introducing infection to our patients. It turns out that it is often better to leave it alone until it begins to become cloudy, then being replaced.' What lesson did hospital staff learned from this experience?