Overnight Ice Factory Explosion Leads to Chemical Hazard, at Least 60 People Injured

[Georgealbert]

Latest update in Thai media, now states there was no explosion.

 

“Updated reports from the ammonia leak at Nong Prue Ice Factory in Chonburi’s Bang Lamung District indicated that there was no explosion, as previously reported, but the leak did lead to more than 140 injuries.

 

The leak has been brought under control, and the cause is being investigated. The owner of the factory said that employees failed to shut down the system when the leak occurred, resulting in the spread of the ammonia.

 

At least three people who smelled the ammonia experienced severe irritation symptoms, while the rest had minor symptoms.”

Have also not seen confirmation as to if the ammonia was stored as, either liquefied under pressure or was refrigerated, I would assume liquefied, as that would be simpler and cheaper.

 

Government safety advice issued, plus my translation.

Edited April 18 by Georgealbert

[Georgealbert]

Video showing how clearly visible the ammonia vapour cloud was.

 

Very little concern shown by those in the video. The car appears to drive through the ammonia vapour cloud and they then experience breathing problems by the sounds of coughing.

Edited April 18 by Georgealbert

[Confuscious]

5 hours ago, hotchilli said:

Yet    again commercial businesses in the residential areas.

Korat does it better.

 

[eyeman]

2 hours ago, Georgealbert said:

Really?

 

This was a simple ice factory, not a chemical plant.

 

I would suggest you never eat out, if they are using LPG, the fire and explosion risk may scare you.

Yes Really. Ignorance award of the year above.

Ice factories can be deadly, Father Joe of Mercy center thought this battle maybe 25 years ago (could be more?) in Klong Toey on behalf of the poor people  affected by ammonia leaks and tragic end result, there is no such thing as a simple ice factory..

Edited April 18 by eyeman

[pizzachang]

6 hours ago, Georgealbert said:

“Ammonia is also flammable at concentrations of approximately 15% to 28% by volume in air.

It disperses quickly.  One of the cheapest, and very efficient refrigerants.  Ice plants use it because it's inexpensive and highly detectable. One thimble-full of liquid ammonia will empty  very large room quickly, as humans will not tolerate concentrations above 100 parts per million. 50ppm is the international exposure level over an 8 hour period (work shift) Humans can detect 5ppm by smell. As long as maintenance is done on valves, piping and compressors, ammonia is safe enough, compared to undetectable refrigerants.  Maintenance is the key [my experience in ice plant maintenance, repair and rebuilding Vilter compressors]

[Georgealbert]

39 minutes ago, eyeman said:

Yes Really. Ignorance award of the year above.

Ice factories can be deadly, Father Joe of Mercy center thought this battle maybe 25 years ago (could be more?) in Klong Toey on behalf of the poor people  affected by ammonia leaks and tragic end result, there is no such thing as a simple ice factory..

5555 so funny, please highlight where I said ammonia was not dangerous.

 

So how would you describe the factory, highly technical, world leading sophisticated operation? It was a simple ice factory making ice using ammonia in a process that is used worldwide. This accident sent 140 people to hospital, mostly for minor exposure, and I am sad to say industrial accidents happen everywhere.

 

The rest of you post seems a irrelevant rant, with nothing to do with this inciden just about a man/priest who once described himself like this “I initially came to Klong Toey as a sort of exile, shunned by the church because of my boorish behaviour. I was drunk; I was always angry about something, an angry young man. I didn’t fit in.”

[kwilco]

 

3 hours ago, Excogitator said:

The regulation (or lack thereof) of indistrial zones and safety in Thailand is a serious and constant risk to public safety. I wouldn't want to live within a 100km of any chemical or petrochemical plant here..

 

well if you live in Pattaya,or anywhere in Chonburi or Rayong provinces then you need to move.

[Georgealbert]

37 minutes ago, pizzachang said:

It disperses quickly.  One of the cheapest, and very efficient refrigerants.  Ice plants use it because it's inexpensive and highly detectable. One thimble-full of liquid ammonia will empty  very large room quickly, as humans will not tolerate concentrations above 100 parts per million. 50ppm is the international exposure level over an 8 hour period (work shift) Humans can detect 5ppm by smell. As long as maintenance is done on valves, piping and compressors, ammonia is safe enough, compared to undetectable refrigerants.  Maintenance is the key [my experience in ice plant maintenance, repair and rebuilding Vilter compressors]

Yes fully agree, it is nice to see someone who understands this is a standard process, used everywhere. I do find that many AN posters, are drama queens, who first and only response is Thai bashing.

 

Maintenance as you say is the key, and in this incident, from the latest update it appears that some valve was left open, causing an overfill/overflow. I have no idea if the shut down to prevent this situation was manual or automatic, or what safeguards were in place, or what went wrong, if it maintenance issue, process issue, part failure or some accident that prevented the shut off. It would be interesting to know your thoughts, on what had the potential to go wrong here.

 

Ammonia as you say, is very pungent and no-one is going to stay for prolonged exposure willingly. My comments are from the emergency response angle, which put in place a worse case scenario response plan. The emergency response guidebook for first responders is produced in Thai, by the Department of Pollution, and I would hope that responders had access to a thai language SDS (safety data sheet) from the safety site, or even their own previous operational inspection.

 

 

[john donson]

in Lat krabang, near the airport, there is an old abandoned football stadium

 

nothing to see, right

 

till I visited a moo baan nearby and the back of the old stadium is now full of chemicals

 

you can smell it from the moo baan

 

an accident waiting to happen

 

on the main street side, it is covered up, so one might not suspect there is now an illegal chemical storage facility

 

 

[Georgealbert]

6 minutes ago, kwilco said:

 

 

well if you live in Pattaya,or anywhere in Chonburi or Rayong provinces then you need to move.

100 km from any chemical processing in Thailand, would be a long way from civilisation.
 

Maybe the poster should consider contacting Elon Musk, no chemical works on Mars, but wait you have that risk of the rocket and the fuel. 5555555

[Georgealbert]

30 minutes ago, john donson said:

in Lat krabang, near the airport, there is an old abandoned football stadium

 

nothing to see, right

 

till I visited a moo baan nearby and the back of the old stadium is now full of chemicals

 

you can smell it from the moo baan

 

an accident waiting to happen

 

on the main street side, it is covered up, so one might not suspect there is now an illegal chemical storage facility

 

 

Yes that would worry me.

 

Chemical are safe is marked, used, stored and disposed of correctly.

 

What you have with illegal storage/dumping, is chemicals that may not be marked, may mix forming new chemicals/compounds, may have unexpected reactions, and no-one will know how toxic, flammable or volatile it is normally or in an emergency, such as exposure to them or fire.

Edited April 18 by Georgealbert

[Georgealbert]

1 hour ago, Confuscious said:

Korat does it better.

 

This is the same worldwide. Countries may have zoning to remove high risk processing from residential areas, but many hazard will still be found. Thailand is not unique with these dangers.

 

An example I will highlight, is from the UK, Buncefield Oil Terminal, Hemel Hempstead, where a large oil terminal fire occurred, and the initial explosion blue out windows in surrounding property.

 

[billd766]

1 hour ago, eyeman said:

Yes Really. Ignorance award of the year above.

Ice factories can be deadly, Father Joe of Mercy center thought this battle maybe 25 years ago (could be more?) in Klong Toey on behalf of the poor people  affected by ammonia leaks and tragic end result, there is no such thing as a simple ice factory..

Ignorance of the year award. Really?

 

Where are all YOUR explanations, diagrams etc referring to what happened?

 

I learned a lot more about ammonia leaks and ice plant from in a few minutes than I could ever learn from your posts in a lifetime.

 

He discussed the subject, provided links and easily understandable drawings.

 

And you discussed and provided what? Just what knowledge did you provide on the subject, other than a cheap and stupid insult?

[kwilco]

33 minutes ago, john donson said:

in Lat krabang, near the airport, there is an old abandoned football stadium

 

nothing to see, right

 

till I visited a moo baan nearby and the back of the old stadium is now full of chemicals

 

you can smell it from the moo baan

 

an accident waiting to happen

 

on the main street side, it is covered up, so one might not suspect there is now an illegal chemical storage facility

 

 

Apparently in Chonburi Rayong over 50% industrial waste is dumped in ground filling that is unprepared or unsuitable for it.

Edited April 18 by kwilco

[Georgealbert]

Seems the factory is back open now, and The Pattaya News are reporting that an employee forgot to close a valve, so manual system with possibly no safe guard.
 

There was no explosion or fire, which seems to be back up by the lack of any structural damage in the pictures online.

 

https://thepattayanews.com/2024/04/18/update-ammonia-leak-at-pattaya-area-ice-factory-under-control-over-160-people-affected/

[PETERTHEEATER]

Considering the number of locals who carry the nasal inhaler (Poy Sian) on their persons, some with one stuffed into a nostril, I should have thought they would be able to tolerate infrequent doses of ammonia gas.

[Confuscious]

1 hour ago, Georgealbert said:

This is the same worldwide. Countries may have zoning to remove high risk processing from residential areas, but many hazard will still be found. Thailand is not unique with these dangers.

 

An example I will highlight, is from the UK, Buncefield Oil Terminal, Hemel Hempstead, where a large oil terminal fire occurred, and the initial explosion blue out windows in surrounding property.

 

France started in the '70's to require that all industries should be moved to a "Zone Industriële".

This had a lot of benefits, apart from the security aspect.

Less or no heavy traffic in the cities; Easy logistics; Easy access to security departments (Fire brigade; Ambulance;Etc.)

[Jan Scooter]

Yeah, ammonia for free. I Never understood why ammonia is so expensive in Thailand

Edited April 18 by Jan Scooter

[TigerGuardian]

10 hours ago, Georgealbert said:

Very little details on what caused the explosion at this stage, hopefully no serious injuries and more details will follow.

 

Seems good procedures to evacuate a wide area, as ammonia is harmful if inhaled or swallowed, can cause lung injury (effects may be delayed). It is corrosive to the eyes, skin and respiratory tract. Can cause permanent eye injury or blindness, and permanent scarring of the skin, depending on exposure.

 

Ammonia is lighter than air, so natural dispersal will occur, and so no chance of build up in low areas. Below for comparison, is an example of the size of the risk/exposure area (i have not used ice factory location). This is from using an emergency hazmat response app, Wiser.

 

Overall, accurate information George. But it must be remembered that while Ammonia has a vapor density of 0.59 (air=1), when a release occurs in the presence of moisture such as rain or high humidity levels, the vapors can become heavier than air.  Thanks for your comments and stay safe. 

[Georgealbert]

15 minutes ago, Confuscious said:

France started in the '70's to require that all industries should be moved to a "Zone Industriële".

This had a lot of benefits, apart from the security aspect.

Less or no heavy traffic in the cities; Easy logistics; Easy access to security departments (Fire brigade; Ambulance;Etc.)

Thanks, good information, and got me thinking.
 

I hope they also reviewed the emergency response at the same time, as moving industries away from police, fire and ambulance stations will increase response times.

 

It also makes it interesting for emergency/crisis planning, with the industrial areas having a high daytime (working) risk profile and lower at night, and the city having a different risk profile, say medium daytime (hospitals, commercial, care facilities) and high at night (residential).

 

French firefighters (sapeurs-pompiers‘) in Paris (Army) and Marseille (Navy) are military, the rest of the country civilian, with about 75 % on call or volunteers, which would pose recruitment problems with a large work force away from the cities and towns, to do those part-time roles.

 

Sorry was thinking out loud and typing at the same time, went off subject, but made me wonder, that it could never work in the UK, but maybe ok for thailand, as many workers are bused to factories from Pattaya and Sattahip everyday, just can’t see the enforcement side working.

[Georgealbert]

5 minutes ago, TigerGuardian said:

Overall, accurate information George. But it must be remembered that while Ammonia has a vapor density of 0.59 (air=1), when a release occurs in the presence of moisture such as rain or high humidity levels, the vapors can become heavier than air.  Thanks for your comments and stay safe. 

Yes agree, I also assume that the storage must be liquid ammonia, so initial spread would be over a wider area.
 

The travel distances of any vapour clouds are also greater at night, this is contained in both the emergency response guidebook (ERG) and Wiser app., and this is based of emission rate and dispersion modelling carried out the US Department of Transport (DOT). If these increased night distances are relevant to conditions in Thailand, it has never been clarified, but better to be safe , than regret it later.
 

Even with moisture the problem of build up of ammonia gas in low lying areas, will not be as dangerous as say LPG, but will still need to be considered as part of the response and inspections/testing carried out. I assume some sort of ammonia (NH3) gas detector was available.

 

Looking at the videos and pictures posted, it appears that water spray containment was used to prevent further spread, it is reported that the leaking valve was isolated or closed, and the water spray maintained until all the vapour had been dispersed.

[Confuscious]

1 hour ago, Georgealbert said:

Thanks, good information, and got me thinking.
 

I hope they also reviewed the emergency response at the same time, as moving industries away from police, fire and ambulance stations will increase response times.

 

It also makes it interesting for emergency/crisis planning, with the industrial areas having a high daytime (working) risk profile and lower at night, and the city having a different risk profile, say medium daytime (hospitals, commercial, care facilities) and high at night (residential).

 

French firefighters (sapeurs-pompiers‘) in Paris (Army) and Marseille (Navy) are military, the rest of the country civilian, with about 75 % on call or volunteers, which would pose recruitment problems with a large work force away from the cities and towns, to do those part-time roles.

 

Sorry was thinking out loud and typing at the same time, went off subject, but made me wonder, that it could never work in the UK, but maybe ok for thailand, as many workers are bused to factories from Pattaya and Sattahip everyday, just can’t see the enforcement side working.

 

Rayong has a similar urbanisation, where most of the heavy industry is located in the Industrial Park.
In several cities in Thailand, industrial zones are being developped in a similar way as the French "Zone Industriele".
Hope that they succeed and move all heavy/dangerous industry out of the city centres.

 

Thai-Chinese Industrial Zone - AMATA

Amata Corporation

https://amata.com

The Thai - Chinese Rayong Industrial Zone has become one of the biggest industrial cluster centers and manufacturing export bases in Thailand and ASEAN for China's traditional advantageous industries, such as new technologies, new energy, new materials, vehicle parts, machinery, and household electrical appliances.

 

Navanakorn Industrial Zone

https://www.navanakorn.co.th

Nava Nakorn, Where the Industry Grow, industrial land thailand,industrial land asia,industrial park thailand,industrial park asia,industrial estates ...

 

 

 

[Georgealbert]

46 minutes ago, Confuscious said:

 

Rayong has a similar urbanisation, where most of the heavy industry is located in the Industrial Park.
In several cities in Thailand, industrial zones are being developped in a similar way as the French "Zone Industriele".
Hope that they succeed and move all heavy/dangerous industry out of the city centres.

 

Thai-Chinese Industrial Zone - AMATA

Amata Corporation

https://amata.com

The Thai - Chinese Rayong Industrial Zone has become one of the biggest industrial cluster centers and manufacturing export bases in Thailand and ASEAN for China's traditional advantageous industries, such as new technologies, new energy, new materials, vehicle parts, machinery, and household electrical appliances.

 

Navanakorn Industrial Zone

https://www.navanakorn.co.th

Nava Nakorn, Where the Industry Grow, industrial land thailand,industrial land asia,industrial park thailand,industrial park asia,industrial estates ...

 

 

 

Yes agree, for heavy/dangerous industries, but would you describe the ice factory involved last night as heavy/dangerous industry. Myself I would not, and believe that it would be practically impossible to move this type of premises out of local communities, because they have been established over sometime, serve the needs of the local communities and commercial businesses and could probably not survive financially if moved away so far.

 

Even in Rayong, not all the heavy industries have moved, for example around IRPC port on the eastern side of the city, and even the other industrial parks are seeing residential development to cater for staff in the factories.

 

I like the idea, but it would need a clear criteria for what industries would have to locate away from cities and towns. Would that be based on factory size, numbers employed, chemicals processes, dangerous goods used, etc.?

 

The leak last night only lead to 3 serious cases that  remain hospitalised for observation,  which is not nice for them, but can not be described as a disaster. More damage was done by the LPG leak/fire, from the kratom liquid seller that destroyed 3 houses earlier in the week. That may sound crass/uncaring, but in terms of crisis management, this was a very minor event, the factory is back up and running as normal today.

 

Thailand would benefit from a better safety culture and inspections, but incidents like this, where human error is being blamed, are very hard to regulate for. It looks dramatic in the news, but will be forgotten by most in a week.

Edited April 18 by Georgealbert

[Confuscious]

5 minutes ago, Georgealbert said:

Yes agree, for heavy/dangerous industries, but would you describe the ice factory involved last night as heavy/dangerous industry. Myself I would not, and believe that it would be practically impossible to move this type of premises out of local communities, because they have been established over sometime, serve the needs of the local communities and commercial businesses and could probably not survive financially if moved away so far.

 

Even in Rayong, not all the heavy industries have moved, for example around IRPC port on the eastern side of the city, and even the other industrial parks are seeing residential development to cater for staff in the factories.

 

I like the idea, but it would need a clear criteria for what industries would have to locate away from cities and towns. Would that be based on factory size, numbers employed, chemicals processes, dangerous goods used, etc.?

 

The leak last night only lead to 3 serious cases that  remain hospitalised for observation,  which is not nice for them, but can not be described as a disaster. More damage was done by the LPG leak/fire, from the kratom liquid seller that destroyed 3 houses earlier in the week. That may sound crass/uncaring, but in terms of crisis management, this was a very minor event, the factory is back up and running as normal today.

 

Thailand would benefit from a better safety culture and inspections, but incidents like this, where human error is being blamed, are very hard to regulate for. It looks dramatic in the news, but will be forgotten by most in a week.

 

"Heavy/Dangerous" industry is not based on solely 1 criteria.
The reason to move industries to an industrial zone is based on a whole list of criteria and is different for every country.
I agree with you that an Ice factory is hardly a heavy or dangerous industry and surely not at that size.

Thailand IS a third world country in many options.
I doubt that Thailand will change in that category in the next few years, but there is always hope.

[Georgealbert]

12 minutes ago, Confuscious said:

 

"Heavy/Dangerous" industry is not based on solely 1 criteria.
The reason to move industries to an industrial zone is based on a whole list of criteria and is different for every country.
I agree with you that an Ice factory is hardly a heavy or dangerous industry and surely not at that size.

Thailand IS a third world country in many options.
I doubt that Thailand will change in that category in the next few years, but there is always hope.

Full and total agreement with your post, Thailand is changing but slowly.

[pizzachang]

5 hours ago, Georgealbert said:

would be interesting to know your thoughts, on what had the potential to go wrong here.

 

Well, as I said maintenance is the key in systems like this. Interesting enough "oil" is essential in maintaining the integrity of piping and valves.  I witnessed an explosion of the ammonia tank at a fish processor in Alaska - across the street from our ice plant - 4000 lbs of liquid ammonia.  The resulted cloud dispersed relatively quickly because of the location in a bay, but the fire took some time to extinguish.  This accident started with an rusty valve in a supposedly unused section of piping. The engineer (a very competent tech that I knew personally) had his mask and an assistant, and were aware of all the possibilities; the threads at the valve broke (corroded from the inside - ammonia is corrosive - much less so if there's enough oil in the system.) and they ran outside and then attempted to turn off another valve that "could" supply that piping, but too late. Neither were injured but did get some serious inhalation - ammonia turn chemically into sulfuric acid when it contacts the moisture in your lungs. We used sulfur "sticks" to locate small leaks and those are terrible to inhale too, but the masks work very well. So, in a guess, a leak unattended, a rusty pipe corroded inside and looking perfectly normal outside, or just not double-checking a refill procedure could have caused this one. The storage tanks are usually regulated and inspected but do require safety valve replacement by time in service, at least in the US.

[pizzachang]

5 hours ago, Georgealbert said:

employee forgot to close a valve,

The most common reason for larger leaks.  We used a check system and even had actual key locks for valves that were normally closed and a tag when you removed the lock to use the valve.  Ammonia does have to be added to the systems periodically, because ammonia does leak, even through the tiniest of openings - the good thing is you can smell a leak at 5ppm and that is when action needs to be taken.

[Georgealbert]

11 minutes ago, pizzachang said:

Well, as I said maintenance is the key in systems like this. Interesting enough "oil" is essential in maintaining the integrity of piping and valves.  I witnessed an explosion of the ammonia tank at a fish processor in Alaska - across the street from our ice plant - 4000 lbs of liquid ammonia.  The resulted cloud dispersed relatively quickly because of the location in a bay, but the fire took some time to extinguish.  This accident started with an rusty valve in a supposedly unused section of piping. The engineer (a very competent tech that I knew personally) had his mask and an assistant, and were aware of all the possibilities; the threads at the valve broke (corroded from the inside - ammonia is corrosive - much less so if there's enough oil in the system.) and they ran outside and then attempted to turn off another valve that "could" supply that piping, but too late. Neither were injured but did get some serious inhalation - ammonia turn chemically into sulfuric acid when it contacts the moisture in your lungs. We used sulfur "sticks" to locate small leaks and those are terrible to inhale too, but the masks work very well. So, in a guess, a leak unattended, a rusty pipe corroded inside and looking perfectly normal outside, or just not double-checking a refill procedure could have caused this one. The storage tanks are usually regulated and inspected but do require safety valve replacement by time in service, at least in the US.

Thanks, so it that situation it was not possible to close the valve, or did the responders try to use any sort of hazmat leak kit or leak sealer?

 

You said the fire took longer to contain, was that because a decision was made to allow the fire to burn,  containing the fire spread, to burn off the leaking gas or because it was a large out of control fire?

 

So would you expect any automatic warning device to detect the leak, or should the area have some form of detection system, or just rely on staff smelling the leak?

 

Sorry to ask, but I have some friends, who are first responders and they like to quiz me on what I would do. Personally I would want as much information from someone at the factory, when doing the initial size up, SDS/hazmat guidance, then a plan of rescues, containment, isolation of leak, vapour dispersal and finally clean up.

[pizzachang]

12 hours ago, Georgealbert said:

it was not possible to close the valve

I'll try and respond in order.  It is quite possible that the valve couldn't be closed (various reasons, including corroded parts inside or simply to much escaping gas) Remember, it's under pressure to keep it liquid. To my knowledge, limited to my years of service ending in 2008, there is no "leak stopper" or sealer. Maybe there is now, I haven't kept up. #2 Ammonia likely was already fully expended from the system in the Thailand leak - up to the next closed valve. In the case of say, a 100 lb. refill tank (looks like a big lpg tank but beefier) a faulty valve or unscrewing past a certain point will be a big surprise to the tech. Once I had an assistant who did exactly that on a routine replenish to our holding tank, and the 100 lbs of instantly converting liquid to gas, emptied in about 3 or 4 seconds. I had time to stop him from trying to rethread the valve - even with heavy rubber gloves, he would have had frostbite or worse. This much ammonia dispersed quickly, but the surrounding businesses complained a lot. By the time the complaints reached the city's manager, even the smell was gone. Remember, 5ppm can be detected but it's not really a danger - think of household ammonia sold in the US ( I never see it in Thailand) The fire was out of control in our situation before the f.d. arrived and the decision was made by them & plant managers to let it finish but contain it to the building. The bad part was the various materials other than ammonia that burned, insulations, paint, oils, and lots of paper/plastic packaging supplies. But the ammonia was long dispersed. #3 Location of sensors, their maintenance would be the factor here. The sensors we used had a industry setting 25 ppm, set in potential leak areas at around 6 feet. They require periodic maintenance to do their job. I'd guess that the leak (Thailand) was small enough to be contained  and don't know if the particular location of the leak could have been tied to any automatic shut-off.  Usually these sensors are tied to a sound warning for the particular area; then any responder had to have the proper gear to enter the area; first to assess the location, turn off adjacent valves or see the situation is serious enough to allow the expulsion to finish and then fix the problems. Remember, NH3 dissipates very quickly and containing an active leak depends on different factors - of responders, equipment quickly available and the actual amount of NH3 that is involved.  A train tank car is much different than a small ice plant's storage or refill vessels. Here's some photos of the one I witnessed. As you can see, the location was about as good as they get for quick dispersion of the ammonia. 

 

[Georgealbert]

18 minutes ago, pizzachang said:

I'll try and respond in order.  It is quite possible that the valve couldn't be closed (various reasons, including corroded parts inside or simply to much escaping gas) Remember, it's under pressure to keep it liquid. To my knowledge, limited to my years of service ending in 2008, there is no "leak stopper" or sealer. Maybe there is now, I haven't kept up. #2 Ammonia likely was already fully expended from the system in the Thailand leak - up to the next closed valve. In the case of say, a 100 lb. refill tank (looks like a big lpg tank but beefier) a faulty valve or unscrewing past a certain point will be a big surprise to the tech. Once I had an assistant who did exactly that on a routine replenish to our holding tank, and the 100 lbs of instantly converting liquid to gas, emptied in about 3 or 4 seconds. I had time to stop him from trying to rethread the valve - even with heavy rubber gloves, he would have had frostbite or worse. This much ammonia dispersed quickly, but the surrounding businesses complained a lot. By the time the complaints reached the city's manager, even the smell was gone. Remember, 5ppm can be detected but it's not really a danger - think of household ammonia sold in the US ( I never see it in Thailand) The fire was out of control in our situation before the f.d. arrived and the decision was made by them & plant managers to let it finish but contain it to the building. The bad part was the various materials other than ammonia that burned, insulations, paint, oils, and lots of paper/plastic packaging supplies. But the ammonia was long dispersed. #3 Location of sensors, their maintenance would be the factor here. The sensors we used had a industry setting 25 ppm, set in potential leak areas at around 6 feet. They require periodic maintenance to do their job. I'd guess that the leak (Thailand) was small enough to be contained  and don't know if the particular location of the leak could have been tied to any automatic shut-off.  Usually these sensors are tied to a sound warning for the particular area; then any responder had to have the proper gear to enter the area; first to assess the location, turn off adjacent valves or see the situation is serious enough to allow the expulsion to finish and then fix the problems. Remember, NH3 dissipates very quickly and containing an active leak depends on different factors - of responders, equipment quickly available and the actual amount of NH3 that is involved.  A train tank car is much different than a small ice plant's storage or refill vessels. Here's some photos of the one I witnessed. As you can see, the location was about as good as they get for quick dispersion of the ammonia. 

 

Many thanks for giving such a detailed and interesting response. My comments are more generic and general hazmat procedures, hence why I said before, at any incident, the on site specialist is the person to advise emergency responders.

 

The hazmat leak sealers kits I have used before, were normally made of plugs, stoppers, patches, bandages, clamps and sealing putty and were designed for sealing up punctures, gashes, cracks and fractured pipes/valves, not relevant in this situation, as this now seems to have been a valve left open, and emptying the tank.