[Shermy]

The NYPD recommends that corporate and institutional security directors review their protection of HVAC systems, parking installations, and security in general

[HAL9000]

review their protection of HVAC systems

So we need gas masks and oxygen tanks. Check.

[Condor51]

The NYPD recommends that corporate and institutional security directors review their protection of HVAC systems, parking installations, and security in general.

I don't know why you highlighted the HVAC part but let me say that professionally speaking, and in plain English - That won't work. You can't commit mass murder that way. There's a gazillion technical reasons I could go into but I don't feel like running an HVAC class now.

As such, someone at the NYPD apparently believes in urban legends. I suggest they contact someone at ASHRAE before they waste a lot of peoples money and instill paranoia needlessly.