(DNAINFO)  Amy Zimmer | December 10, 2016 — Steam heat experts say that issues with valves are not uncommon in New York City buildings.

After two infant sisters were tragically killed in a Bronx apartment because of a problem with the aging radiator, many New Yorkers are now paying more attention to their own steam heating systems.

A weakened valve on the radiator is believed to have caused the accident in the first-floor bedroom where 1-year-old Scylee Vayoh Ambrose and 2-year-old Ibanez Ambrose were napping at 720 Hunts Point Ave., sources told DNAinfo.

Sources believe the valve had weakened due to normal wear and tear and may have fallen off when the heat was turned on, unleashing scalding steam into the room.

Though such “freak accidents” may be rare, steam heat experts say that issues with valves are not uncommon in New York City buildings, where old steam heat systems are often out of balance, causing some apartments to be too hot and others to be too cold.

Because of this, apartment dwellers or superintendents often look for quick fixes that might do more harm than good.

Here’s what to keep an eye on if you have a steam heating system:

Source: What to Look For to Ensure Your Radiator is Safe – Hunts Point – DNAinfo New York