Sorry to hear about the trouble you had with your Nest Protects.
Nest Protect can sometimes be set off by sources of steam, if enough steam enters the smoke chamber.
In the event of an errant alarm you should be able to silence the alarm horn by pressing the Nest button, or waving at the Protect on the wall. You can find more information in the article below.
If the steam carried particles into the smoke chamber, this could explain why the alarm kept sounding after the steam was cleared.
We'd like to take a look into this and help make sure everything is working properly.
Please give us a call at 0808 169 2307. We're open Monday to Friday, 9:00 to 18:00 GMT.