Hi, Last week our carbon monoxide detector was going off after shower and stopped after we re-plugged. Immediately we bought a new digital detector and checked, everything is perfect. Again from yesterday after shower the old detector is beeping (It will stop if we unplug and plug again), and the new one is not going off. Our land lord said it is fine as the new one is not going off. We are worried anyway. Please advice in this regard.

Carbon monoxide detectors are only supposed to activate when they sense carbon monoxide, it is NOT normal for it to activate when the shower is on.

To be sure you could put the new CO detector adjacent the old one, turn on the shower and see what happens. From what you have said the old one will sound, which would indicate it has a problem (Check its age, as CO detectors last 5-7 years) I doubt they will both sound.