Fire Fire Fire Alarm

[Gina Marie]

I recently had my turbo blankets changed. The new blankets on the 6v92 gave off a burning ordor. The salon and the engine room after and during use had this smell but it is wearing off after being installed for three days. Today after travel from Hillsboro inlet to Boca Raton inlet appox. 10 miles or so or about 30 minutes of travel at 1800 rpms upon entry to the inlet my fire alarm went off. Talk about priority, navigating the inlet with an out going current and the fire alarm indicator warning light and buzzer sounding, I had my hands full. Once I navigated through the Boca Raton Inlet bridge and was out of the pull of the current I immediatley stopped ran down stairs, I first opened the fire port hole and no smoke and no heat. I then openned the hatch slowly and again no smoke and no heat. Smell and a slight haze yes. This all happened with 5 minutes.

The fire system is connected to heat detectors in the engine room. Heat detectors are fused items and to trip they need heat, once tripped sinced fused system should not reset. Is that right??????????????????????????

After a few minutes the system reset.

How does this system work?????????

Why would the fire system trip and reset.?????????????

I have a Halon system and I don't think I have smoke detectors.

Is it a coincidence that the smell from turbo blankets and a faulty fire buzzer all happened at the same time.

What makes the fire warning buzzer and light trip??????????????????

Confused Gina Marie /Tom .

My warning light on the helm continued to remain on that with the buzzer.

 

[captddis]

You probably have the temp sensors mounted under the salon sole. There are probably a couple. It is just a temp sensor and will come on when temp gets to 160 [I think} and go off when the temp comes down. It sensed heat so determine why! Maybe a exhaust leak or a gap in the new blanket. If needed run the boat and have someone monitor the engine room to determine the cause.

 

[Gina Marie]

Thanks for the advise can you tell me what is a salon sole?

 

[captddis]

The floor in the salon.

 

[Nonchalant1]

Be careful watching in the engine room if you have a halon system. If it thinks there's a fire and goes off while somebody is in there, they can be snuffed out like a fire! I MEAN DEAD....SNUFFED OUT. You only get a few breaths of CO2 or halon, because there's no oxygen in what you're breathing, before you pass out. If you pass out in the halon or CO2, it's all over.

My CO2 system just senses heat, and it sets off the 75 lb CO2 tank first and that tuns on the helm station fire alarm. The reset is a manual push button on the CO2 pipe pressure sensor. Yours is obviously different.

Doug

 

[Genesis]

My boat has two heat sensors in it.

One of them was in a VERY bad location. Right near an exhaust elbow. Run hard, in warm enough weather, and it would trip. There was no fire, but man, the first time that happened it got my attenton FAST!

I moved it. No more problems.

Check carefully to make sure you don't have a gap in a blanket or a real hazard. If your system is like mine it has no connection to the fire bottle at all. Its just a heat alarm in the engine room, and SHOULD go off at 160F.

Sometimes people change these out for 125F sensors. That's a bad move; the 160F ones are correct for an engine room. 125F is quite easy to hit in an engine room on a hot summer day!

The switches are Airpax thermoswitches and self-reset when they cool down.

Oh, on the fire extinguisher, the CO2 is bad news if it goes off. It will both get you by asphyxiation and also will reduce the visability in the compartment to zero from the vapor cloud (it will basically SNOW Co2 in there!) along with causing extreme frostbite if you get hit by the discharge. Bad all the way around if you're in there when it goes off.

REAL Halon (e.g. 1211) will not kill you. However, if it gets hot enough being used on a real fire, the products of its decomposition can (its a phosgene-like compound!) so you don't want to be in there when it goes either.

FE241 and related "new" clean agents are an unknown. Some are supposedly human-safe, others not.

I don't want to be in the compartment with a discharging fire bottle no matter what's in it.

 

[captddis]

Co2 will definately kill you. Halon is generally safe unless it gets run through a diesel engine then the exhaust is poisinous. I know a couple people who had halon discharge when they were in the engine room, other than being startled suffered no harm. I treat Co2 systems with respect and let the pros arm them.

 

[Liquid Asset]

Genesis,

I was trying to figure out how the light/buzzer on the dash worked when I had the fire inspection done this year. The fire guy was setting the bottle in the discharged mode, but it was not setting off the light/buzzer on the dash. BUT, the test light shows it was working. I am now thinking that hte temperature sensor (Round Red Dome) mounted on the salon floor is what you are refering to. I have the CO2 Kiddie system. Does that sound like what your system was before you changed to the safe fire suppressent

 

[Genesis]

No - the round red dome only fires the CO2 bottle. Look for a small (about 2-3" diameter) plastic sensor with a ~.5" metal cap in the center. Those are the heat sensors and should have two wires going to them. On my boat they are completely separate from the fire bottle system.

I have a "you're on fire" alarm (heat sensors) and then a separate "the fire bottle just went off and hopefully the fire is out" alarm.

 

[MikeP]

I think CO2 may be getting a bad rap that it doesn't deserve.

CO2 is an EXCELLENT fire supressant. It leaves no residue, will shut down an engine automatically, and is completely non-toxic.

Just like any inert gas, when it displaces the air in the room, there is no longer any oxygen to feed the fire or to breathe. So you can pass out for lack of oxygen, but not due to any toxicity of the CO2. You can breathe CO2 just fine if there is sufficient O2 in the mix to sustain life. But the whole point of the system is to ensure that there is NOT enough O2 to sustain the fire (or you).

Obviously, as has been much stated, if you are in the engine room when the system discharges, you need to leave. It's not like you are going to immediately fall over but you NEED TO LEAVE immediately and get up on deck.

The disadvantage of CO2 is that it takes a larger bottle to provide the same coverage of "newer" chemicals and is therefore more expensive to use/refill, more difficult to man-handle for weighing or other purposes and it takes more space. The only reason I would consider replacing the CO2 system is if the bottle itself is no longer capable of passing inspection. Since our 53 (I assume all Hatts?) has a separate engine shutdown that is triggered if the fire system activates, there is no need to add that capability which is required with a non-CO2 system.

 

[Genesis]

I think CO2 may be getting a bad rap that it doesn't deserve.

CO2 is an EXCELLENT fire supressant. It leaves no residue, will shut down an engine automatically, and is completely non-toxic.

Just like any inert gas, when it displaces the air in the room, there is no longer any oxygen to feed the fire or to breathe. So you can pass out for lack of oxygen, but not due to any toxicity of the CO2. You can breathe CO2 just fine if there is sufficient O2 in the mix to sustain life. But the whole point of the system is to ensure that there is NOT enough O2 to sustain the fire (or you).

Not true.

CO2 is inherently poisonous to animals - including humans. Just ask all the corpses who have become that way diving recreational rebreathers when they have a scrubber breakthrough.

Lots of O2, but too much CO2. If you're lucky and the problem comes on slowly you get a really severe headache as a warning. With high enough levels though you may not have enough time to notice before you pass out.

Extinguishing Mechanism of Carbon Dioxide

Flame extinguishment by carbon dioxide is predominantly by a thermophysical mechanism in which reacting gases are prevented from achieving a temperature high enough to maintain the free radical population necessary for sustaining the flame chemistry. For inert gases presently used as fire suppression agents (argon, nitrogen, carbon dioxide, and mixtures of these), the extinguishing concentration (As measured by the cup burner method (NFPA 2001)) is observed to be linearly related to the heat capacity of the agent-air mixture (Senecal 1999).

Although of minor importance in accomplishing fire suppression, carbon dioxide also dilutes the concentration of the reacting species in the flame, thereby reducing collision frequency of the reacting molecular species and slowing the rate of heat release (Senecal 1999).

.....

Cite: http://www.epa.gov/ozone/snap/fire/co2/co2report.html

The problem with CO2 from a life-safety perspective in a boat engine room is that when it discharges it produces a "white-out" condition that reduces visability to zero almost instantly and the very high noise levels associated with the release are severely disorienting. If you are hit directly with the discharge you are also very likely to suffer extreme frostbite on whatever surface of your body is involved.

From the instant of discharge to loss-of-consciousness is less than 1 minute at fire suppression levels, and even if you get clear of the space where the discharge took place you may still pass out, since it takes time for your body to clear the CO2 load. Without artificial respiratory support until your body clears the CO2 from the bloodstream and tissues you're screwed. Provision of high FO2 (e.g. a demand-mask providing 100% O2, or a scuba regulator attached to a decompression cylinder full of 100% O2) will not prevent respiratory arrest post-insult; however, ordinary artificial respiration will sustain life until your body can clear the load and prevent death.

On recreational boats there is a very real risk with these bottles due to the lack of a discharge delay and often-present convoluted spaces into which you may have crawled to do something at the time. If you're contorted into one of these little spaces and a CO2 system goes off, you're in big trouble.

I like CO2 as an extinguishing agent but you must treat it with respect.....

 

[MikeP]

Well, I learned something today! I had no idea that CO2 was in itself toxic at all. We were lucky to survive all those CO2 extinguisher fights when I was a high school summer worker in a shipping warehouse. I don't think there was a single charged extinguisher left in the place! Then there was all the grade-school playing with dry ice...

I should have done some research instead of making assumptions based on using CO2 for teenage combat, cooling beer, and general hi-jinks!

Since reading Karl's post I have learned that in 1986, an upwelling of CO2 from Lake Nyos in Cameroon killed 2000 people. I have always assumed that any death from CO2 was caused by the lack of O2, not the CO2 itself. In fact, when folks have made statements that CO2 killed someone, I thought they were confusing CO with CO2. Obviously I was totally wrong.

I hate it when that happens!

 

[Genesis]

The human body is a funny thing.

CO2 buildup is what causes you (unless you've got severe respiratory disease!) to breathe. But its not really CO2 - CO2 dissolves in water to produce carbonic acid, and that's what is actually transported around your body. It is then eliminated as CO2 from the lungs.

You'd think that oxygen deficiency would be what triggers breathing. Its not. You can actually achieve full oxygenation of the blood with a PO2 as low as 0.16, which is a almost 25% deficiency from the normal level of 0.21 in air at sea level, assuming you're not doing too much work. Loss of consciousness usually occurs around a .11 PO2. When I am diving and doing decompression I will intentionally breathe 100% O2 down as far as 20', which results in a PO2 of 1.6 (the maximum "safe" limit for short-term exposures.) My breathing rate is the same on that very high oxygen content gas as it is on regular air - that's because respiratory drive (in a person of normal physiological function again) is not triggered by the O2 content. This is done while diving to eliminate inert gas - nitrogen (and helium) from what you breathe, which increases the rate of elimination of that inert gas from your tissues - thus, it reduces the time you must stay down to avoid being bent.

What triggers the breathing reflex is a very small shift in the pH of your blood - your body's autonomous systems are hypersensitive to blood pH, and so as more CO2 is retained in your blood as carbonic acid the pH falls and you are driven to breathe faster. As the CO2 level falls your blood becomes more alkaline and your drive to breathe subsides. The changes in a person who is in reasonable health are very small, but they result in extremely accurate control of blood pH - and CO2 content.

But - you can screw this mechanism up. If you forcibly hyperventilate long enough you can drive the pH down low enough to actually cause you to get very close to passing out! If you were able to continue you probably COULD pass out. You'd think that'd be impossible, since you're eliminating all the CO2 in your body - but its not. Some CO2 in your body is actually necessary!

Likewise, if your blood pH drops too low, the system malfunctions on the OTHER end, and instead of causing you to breathe more rapidly it actually shuts down your respiratory drive. You suffocate and die, even though there's lots of oxygen in the air.....

The other wild part of this is that if you freedive you have to be VERY careful with hyperventilation. You can drive your CO2 level down low enough with forced hyperventilation so that you during your freedive you have no urge to breathe even though the PO2 in your body has dropped dangerously low, especially as you ascend. This can cause you to have no urge to surface and get a breath at all up until the point that you actually pass out and drown! People get killed all the time this way freediving due to what is called "shallow water blackout".

If you happen to have a CO2 bottle go off and someone's in the engine room, they may well pass out almost immediately. GET THEM OUT OF THERE and if they are not breathing provide ordinary mouth-to-mouth rescue breathing. Provided that you get to them and restore airflow to their lungs before there is significant tissue damage, they'll coime around in a few minutes and, other than having a hell of a headache, be ok.

 

[MikeP]

As a result of this thread, I asked the System Techs at a large FAA air traffic control facility about the fire systems. There are large inhabited areas as well as large computer rooms. The building was constructed in 1963. I was informed:

CO2 was NEVER used as a automatic system due to the danger to personnel! Originally there were water sprinklers + numerous large (250lb-charge) CO2 bottles with 75ft hoses on reels. The hose could be dragged to a fire location the nozzle pointed as appropriate, and the CO2 triggered manually.

Then, in the 80's came automatic Halon systems - all the CO2 extinguishers were removed. The automatic system had a 60 second audible alarm prior to the Halon being dumped. I'm told that in a system test, with freon substituted for Halon for test purposes in the computer room, it sounded like a 747 going over your head, blew most of the ceiling tiles off their tracks, into the attic and then onto the floor, and scattered every piece of paper that wasn't glued down, including what was in the trash cans. They said you couldn't see into the room for 15 minutes and the room temp dropped 30 degrees!

In 1998 the Halon was removed (thank you, tree huggers ). Now there are only automatic water sprinklers in all areas, including the computer and electronics areas, and a bunch of small portable dry chemical extinguishers all around the building.

The one scary point Karl brought up which I had never considered was an accidental trigger while in the engine room doing some work curled between the engine, collector, and raw water seacock. If that happened, it's probably unlikely that I could get out before the lack of O2 rendered me unconcious, follwed by my death some time later from the CO2 if the lack of O2 didn't kill me first!

 

[Traveler 45C]

As a result of this thread, I asked the System Techs at a large FAA air traffic control facility about the fire systems. CO2 was NEVER used as a automatic system due to the danger to personnel!

That guy is misinformed. I am right now sitting in a building that houses the Air Traffic Control Schools for the Navy (lots of FAA Regs apply and lots of people) and our fire suppression systems are CO2. There is a time delay to allow everyone to clear the area.

 

[MikeP]

Well, that's interesting.

I'm absolutely confident in the tech's statements about the history of the systems. But his recollection about WHY CO2 was never used could be wrong. I recall in the Army that there were all sorts of auto-triggered CO2 systems, similar (but bigger) to the one on my 53, but that was a long time ago...

 

[Genesis]

The interesting thing is that for personnel-inhabited spaces large areas require a pre-discharge warning system with a manual timer override (you hold the button, the timer STOPS)

I've been in a computer room that had a halon system go off when there was no actual fire. It was not funny...... either in what it did to the room or in what it cost to have it recharged. Nowdays, of course, you can't install such things.....

 

[jim rosenthal]

Karl is correct on this. An interesting corollary to all this is what happens to people who don't have normal respiratory function and normal respiratory drive. The most frequent example I see of this is patients with chronic obstructive pulmonary disease (emphysema), whose lung function is poor (reduced diffusion capacity). They will typically have pCO2s in the 55-70 range. Those patients, whose respiratory centers are used to having a pCO2 that would make most of us breathe very briskly indeed, depend on dropping pO2 to induce respiration. Typically what happens is that someone gives them too much oxygen (usually an EMS provider, who are trained to give oxygen quickly and amply) and, since they depend on hypoxic drive to breathe--they stop breathing.
We see patients occasionally who have respiratory disease that causes high pCO2s- we used to see this more with cystic fibrosis, for which the treatment has improved-- and I can tell you that when your pCO2 is high, there are all sorts of problems that accompany it, even with a normal oxygen saturation. And these are folks who have this chronically and are used to it- for someone not chronically ill who all of a sudden had a very high pCO2- well, they wouldn't do well, and very quickly.

 

[Gina Marie]

Genesis, is the following scenerio possible:

When running at 1800 RPM for 30 minutes or more and due to a hazzard like a problem in the inlet I have to power down very quickly rather than gradually. Does this effect the sensors( on the fire monitoring system )were they do not get a chance to cool down because of the immediate power down of the engines an the inability of the water pumps to cool down the turbos gradually.

Just a thought

Thanks

Gina Marie/Tom

 

[Genesis]

Genesis, is the following scenerio possible:

When running at 1800 RPM for 30 minutes or more and due to a hazzard like a problem in the inlet I have to power down very quickly rather than gradually. Does this effect the sensors( on the fire monitoring system )were they do not get a chance to cool down because of the immediate power down of the engines an the inability of the water pumps to cool down the turbos gradually.

Just a thought

Thanks

Gina Marie/Tom

Yes. Temperatures will spike in the engine room when you do this. Mine do (I have a wireless thermometer sender in there over the genset - my "hot point")

HOWEVER, if they're going over 160F I'd be VERY worried, because most fire bottles will go off around 170-175! You're dangerously close to having an unscheduled discharge, and that would make me veeeerrrrryyyy nervous. At best it will ruin your boating day if it happens.

Find those sensors! They're somewhere. Someone may have changed one out for a 125F (normal household type) at some point in the past instead of the 160F (kitchen or machinery space one) that should be in there.

The other possibility is that you really DO have a heat problem down there. Get one of those wireless thermometer senders and stick it in the ER, then go for a run and see what's up.

On the other half of the topic I was going to bring up the O2 provision problem that Jim referenced. See, pure O2 (or as close as you can get) is the standard first aid for dive injuries. There's the issue of someone with COPD possibly going into respiratory arrest if you provide it; the reason that divers feel relatively "safe" about this course of action is that if you have COPD to a degree where this sort of thing is happening its VERY unlikely that you're well enough to go diving in the first place.....