atcomsystems.ca/forum Forums General Telecom News Serious Fire Safety Concerns/Cables from Offshore Manufacturers

We use very little plenum here in Maine but 1 job I did that required it was a medical building. My little 2 pair plenum ran beside miles of pvc drain pipes.

little 2 pair plenum ran beside miles of pvc drain pipes

Non-scientific, but you are talking about the difference between a sheet of paper and a 2x4; both will burn, but the paper (and the thin PVC insulation) catches quicker and spreads faster. (I am curious as to the scientific explanation for Ed's comment that Plenum burns vertically, but not well horizontally while riser is the opposite).

Merritt, it all depends on the thinking of the jurisdiction and law makers. We have areas here that flat out prohibit the use of PVC pipe and conduit within a commercial building. That wasn't always so.

Back in the early 90's there was a bad fire at a hotel/conference center and many people, many of them corporate execs there to attend meetings lost their lives. This wasn't an old structure, it was a spread out 2 story with several large conference rooms owned by a major hotel chain.

The fire was believed to be deliberately set in one area by someone pouring an accelerant on an area of the carpet in a conference room. The fire spread up into the dropped ceiling and toxic smoke and fumes from burning plastics spread throughout the building corridors before the occupants could be evacuated.

Right after that the jurisdiction took a hard look at their fire codes and made major changes. So maybe you just haven't had many unfortunate incidents like this to motivate them.

-Hal

Afaik, plenum burns hotter than riser cable but produces less smoke and toxic fumes. CMP can be substituted for CMR in a riser.

I have mixed feelings about the wire ratings and fire potential. One part of me says always use the correct wire and firestopping (the one I listen to).

The other says 'If the fire reaches the v/d/v cabling, the building is already a total loss (and the occupants in serious trouble) since the sprinklers have failed' and 'why bother running the correct wire when they are going to load the building with cheap Chinese furniture that will turn into liquid accelerant/release toxic fumes once it catches fire'.

Anyway, thanks for the heads-up on the crap cable, Hal.

Is there any reliable "field test" for firetesting cable? Like hanging a 10' piece up and taking a torch to it and timing how long it takes the fire to spread? I know we shouldn't have to do this, but I'm just curious... and have lots of scrap cable laying around.

Jack

Soap box time:

Jack, we could do our own field tests for entertainment, but that doesn't mean a hill of beans in the grand scheme of things. We have to provide/install what is required to cover NEC mandates and local adaptations. I don't agree with many of today's requirements, in fact some of them come off as being downright silly. I'm not educated in the myriad of applicable fields associated with this subject, so I can only speak from personal opinion.

I do remember the day in 1975 when one of New York Telephone's (Verizon today) central offices erupted into flames and burned for several days. This was a huge central office in a mid-rise building. It was determined that the enormous amount of PVC cable caused much of the flame spread. Many of these cables were installed as risers from the underground cable vaults to the distribution frames up to a dozen floors above. This building was full of nothing but CO switching equipment and cable. I'm pretty sure that the fire was caused by a cable maintenance technician using a breakdown set without having taken the necessary safety steps in advance. (That was hearsay from NJ Bell guys at that time, so I can't say for sure what caused it).

The massive spread of this fire spawned the rush to come up with "fire-proof" cable. I really doubt that much technology went into this product development. Truth be known, I'm not so sure that much has been done since then to truly prove the fire safety of plenum vs: non-plenum cable. We've just been fortunate enough to not have many massive fires similar to the one that started this movement.

Another central office fire in Illinois Bell's Hinsdale office many years later spawned even deeper exploration into different cable insulation compounds for different atmospheric conditions. This fire in 1988 likely led to the development of different types of plenum-rated cable. Yes, there are different types of plenum cable now and not all are acceptable in all plenum environments. :bang:

I must say that despite the fact that NYT's central office fire was probably the worst in telecom history, there was another one in 1965 in GTE's (also now Verizon) Richmond, Indiana central office. I think that this one was the true head-turner with regard to fire safety with cabling. Although Richmond was a fairly small-town CO, it was also a toll center. The mechanical equipment took up a lot of space in the building. This fire resulted in the building being a total loss, along with loss of the switching equipment and subsequent phone calling for much of Eastern Indiana. My guess would be that this was the first point at which telcos started seriously thinking about cable being a fire risk. Even rival Bell from as far away as Chicago stepped in to help GTE get this office back into service. They recognized the risk and needed to study what had happened. It took nearly 10 years before things started to change.

The flame spread characteristics that I mentioned earlier in this thread were from a video that I saw during a CEC course I took to maintain my electrical contractor's license. I think that it was produced by Underwriter's Laboratories.

I do feel that many of today's code requirements are a bit backward. I would think that once the fire has penetrated the ceiling space, the burning plastics in the flooring materials and furnishings below would likely be much more of a threat than the phone and data cables. If anything, these cables would likely be the last things to be exposed to the fire.

This subject is probably one that will rival the chicken or the egg question. Yet another of my late-night novels. What can I say?

Here are a few links if you are interested:

What if it happened today?

Wikipedia\'s story

Pretty weak link to the Richmond, IN CO fire.

Okay, Ed....now that you are done with the "BOX", please pass it over here.......


Several years ago I did a hospital in Philly....it had all kinds of regulations dictated not only by the city inspectors but after they got done the state hospital inspectors had to approve it before the rooms could be occupied.

Fire stopping was unbelievable....vertical as well as horizontal....and we are talking miles of fiber, innerduct, and plenum cable with risers of multiple stories.

We brought in 3M fire stop engineers and had a three day class on......*drum roll, please*.....fire stopping.

What type of stop to use, where to use it, and how certian things in the risers burn....or melt.

Done correctly it will stop a real fire.

Now, I was not at all the fires in C O s you spoke of....but I was a Bell employee for the NYC one....what these newbies don't realize is that one was the old cloth, silk, cotton wrap cable. Packed as tight as fire wood. Once it started it just couldn't be put out.

The newer ones where the PVC cable we are used to seeing....burn like car tires....again, packed tight in the cable trays and burned forever.

The only bad office situation I was around was after the fact....a splicer lit a torch in a manhole just outside the cable vault...and it was full of gas. The roof went up, the walls went out, then the roof came back down.

Other than not being able to hear and missing his eye brows, he was fine. But for some reason he didn't want to work manholes anymore.....

Don't leave yourself wide open for law suits or be the cause of someone losing their life.

Ed, *passing back the BOX*....here's your soap box no worse for the wear....

What Ken & Ed said.

Firestopping (or rather the lack of it) is one of the most abused parts of cable placing that I see. 3M does an excellent job with their products. When I worked extensively in Verizon buildings (1995-2003) I was required to take a 2 or 3 day course on what they required for fire safety/ firestopping/ cable placing / cable lacing etc.

I was appalled when I worked in the COs though to see the absolutely hideous electrical work that their own staff performed. When they contracted work out to the local sparkies it was all done to code. When they did it themselves it was an abomination. They bent no pipe whatsoever -everything was done with boxes or condolets or worse. The pipe was usually undersized and the supports were awful or sometimes nonexistant. When I inquired about it I was told that, as a utility, Verizon was allowed to perform their own electrical work and was not under any regulation INCLUDING the NEC.

Most of the (bad) work that I saw involved situations where a series of racks for a specific purpose (new carrier equipment, test bay etc) were installed and the electrical was done by at the same time, perhaps by the same people.

Ken, I'm amazed that a splicer lit off a torch in a manhole! No gas testing, no venting? And an open flame! We couldn't smoke within the perimeter line ABOVE the manhole. Even when we were wiping sleeves, we always heated the solder above and lowered a pot of hot solder down (a little scary for the guy below, but...).


Sam

Sam,

3M is probably the residing king of fire stop. The training had a movie showing a riser with a fire under it being hit by a fire hose....forcing the flame upward into the next floor! So the correct, not just, fire stopping is very important.

You are so very correct about the "utility" statement but we were restricted to the DC side of the wiring.

As far as manholes, slightly off-topic, I was taught the same as you....pot wiping. But the Independents figured if it was safe for you it was safe for a torch....it had been checked for gas prior to lifting the lid. Once the lid was raised and the manhole exhausted, it created a draft. The natural gas was drawn into the vault trench and into the duct bank to the manhole...the blast followed the gas back into the building. It was a gas leak from a pipe ... not the normal ground gas. The CO was full of gas so it was the one that blew.

Back on topic, same wire, different coating, how "clean" it burns, and how unhappy the insurance company will be. Some countries allow criminal prosecution for violations that cause death......

Ken -

At GTE we were also restricted to DC power. All the AC wiring was to be done by a licensed electrical contractor. But this stuff! Horrible! A fire waiting to happen.

Sam

Thanks Ken, Sam and Ed.

Not to get too off topic here, but for Ed: wouldn't it be more prudent to install a newer Halon or CO2 fire suppresion system in a CO building rather than trying to make "fire proof" cabling?

Jack