what is the high pitched whistling noise that lasts for 10 seconds almost every hour on the 40min mark? Does it have something to do with the ammonia alarm? Either one wasn't made in the sales brochure or the website...
I think its coming from 1999 William St. Thermetco: http://www.thermetco.com/en
Here's whats inside the plant :
They were here first, i wont complain, but just want to know where the noise is coming from and what is normal. any ideas?