What makes an Ammonia leak notifiable?
In short, unless you know the local concentration, Ammonia leaks must be reported to Worksafe and they must also be investigated internally.
This is a tricky subject that will no doubt spark some debate from separate corners of the industry and government. Education on the matter does need more visibility not to mention further discussion, clarification and possibly the setting of firm parameters from the legislator to avoid confusion. It is of course difficult to draw a line in the sand as there are many variables at play, which as mentioned can be argued, hence it is why it is best to simply set the differentiation as basic as possible; an uncontrolled leak is notifiable. Here we will try and provide an explanation as to why it is necessary as well as explain the benefits as a business.
Under the Health and Safety at Work Act 2015, Section 24, (1) "a notifiable incident means an unplanned or uncontrolled incident in relation to a workplace that exposes a worker or any other person to a serious risk to that person’s health or safety arising from an immediate or imminent exposure to" — (In relation to Ammonia leaks)
(a) an escape, a spillage, or a leakage of a substance; or
(d) an escape of a pressurised substance.
The key words here are "uncontrolled" and "unplanned" simply a leak or accidental discharge. Releases that have occurred through general maintenance activities will be in a controlled* manor, therefore they should be limited to trace gas; during hose disconnection or during purging and evacuations. They are not considered notifiable unless a worker was exposed or may have been in alternate circumstances exposed to a harmful concentration that could or could have caused harm.
*A controlled but intentional discharge to atmosphere is another topic all together. (Resource Management Act)
Our interpretation of the act is that worker(s) have to have been exposed or if under different circumstances, worker(s) were present during an uncontrolled release they would of been harmed. There is of course the element of the unknown, a majority of leaks will be reported/measured from a distance of the source and possibly not accurately measured. It is not scientific to state that a leak on one end of the engine room was the same concentration as what the fixed gas detector recorded on the SCADA if it were positioned on the adjacent perimeter? Unless the leak was sighted, as in witnessed droplets, fizzing, two phase flow or concentration, we are unable to understand how severe it may or may not have been. We must in that instance take the worst-case scenario and report the incident. This is by sure the safest stance.
What level would cause harm?
Firstly there are burns and irritation to eyes and skin to consider from all types of Ammonia leaks, but liquid and Aerosol leaks are particularly nasty for burns. Even a small low-pressure liquid Ammonia leak could get in to someone’s eye if they were standing in front of it. Likewise, a small vapour plume could makes it way to what I will describe as moist tissue and form highly corrosive Ammonium Hydroxide solutions. Inhalation is where it gets interesting, it confirms the importance of monitoring the atmosphere of your refrigeration system
Using the workplace exposure standards (WES)
25 parts per million (ppm) is the allowance of 8 hours human exposure to Anhydrous Ammonia. This is called the TWA or Time Weighted Average. Provided the TWA has not been exceeded already, 35 ppm is the allowance for Short Term Exposure and is significantly shorter, just 15 min, this is called the STEL. Unless a worker(s) have donned and started respirators they must vacate the area above the STEL. In a production setting - this would prompt an evacuation and lost time.
Using less than the WES guidance as a potential notification threshold is in my opinion very conservative. Not a lot can go wrong here, you will get a stronger concentration from a mopping your floor with household cloudy Ammonia solutions. Furthermore, there is plenty of time allowance here to remain in safe concentrations. You could essentially make a cup of tea sit down and drink it with a piece of short bread before having to officially vacate the area. But what seems safe to me is different to what seems safe to you. A parameter can not be subjective.
According to the U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES There is no evidence that suggests Ammonia is a carcinogenic & or has contributed to any birth defects. There has also been no medical studies that are conclusive in the long term respiratory effects of repeated exposure. Ammonia can not be absorbed through the skin & will not accumulate in the body as it is neutralized & released via the urinary system & exhaled through the breath, however it is paramount respiratory protection is worn in any elevated concentrations not typically found in nature.
Workplace Exposure Standards should not be considered gospel, some that were considered acceptable in the past, are now considered dangerous as well as inversely, some, once were considered dangerous are now getting elevated such as the IDLH, which I understand that there is a recommendation from an industry standard setting body to increase it to 500ppm. We are designed to breathe clean air and all steps should be taken to mitigate the effects of airborne contamination regardless of how strong it is. This includes both engineering and administration controls as well as personal protective equipment.
Use of Immediately Dangerous to Life and Health (IDLH) - 300ppm
In the 1970’s the United states Occupational Safety and Health Administration developed Immediately Dangerous to Life and Health (IDLH) as a respirator selection standard. "An atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an immediate threat to life or would cause irreversible or delayed adverse health effects or would interfere with an individual's ability to escape from a dangerous atmosphere" (29 CFR 1910.120).
IDLH should be an instant trigger for notification, it is clear that as the description suggests it is dangerous. It is also uncomfortable to be in an atmosphere at this concentration, even for persons that are well assimilated with Ammonia’s sharp odor. It is not serious as yet, you will not die or collapse nor will you have any long term health effects as far as what science can provide evidence for but it is in fact dangerous to be around for extended time frames. It will initiate panic and it will most definitely inhibit safe egress for the un-assimilated. But what if it is 200ppm?
Use of Acute Exposure Guideline Levels (AEGLs)
Developed by the US defence force and EPA; Acute Exposure Guideline Level (AEGLs) are values that are intended to protect most individuals in the general population, including those that might be particularly susceptible to the harmful effects of the chemicals
|Exposure level||10 min||30 min||60 min||4 hr||8 hr|
|<AEGL 1 – |
|<AEGL 2 – |
|<AEGL 3 – |
>AEGL 3 –
Looking at the AEGL table, one could argue that using Acute Exposure Guideline Levels would be a good place to set notification set points. We must also include that Ammonia’s self-warning attributes go out the door somewhat, once exposed for a length of time. This is due to olfactory fatigue or your noses inability to distinguish odour after prolonged exposure. This also plays a part in to what is considered strong to someone new to refrigerant grade Ammonia vs an experienced engineer’s view that it has invigorating properties.
As you can see there is good scientific evidence available to warrant setting a parameter but unless Worksafe New Zealand can set a standard concentration (ppm) or demarcation for reporting, it is advisable to report all leaks from your Ammonia refrigeration system. If you can provide good evidence that it was safe, it is likely that you may as well have taken the five minutes to also fill in the form online as you have already completed an investigation.
Investigating and recording Ammonia leaks is very good metric to have available for managing your system. It is a measurement of how mechanically secure your system is, it is also a measure of how well maintained it is. The older system the more leaks you can expect, modern equipment has better seal configurations than past designs, but all systems will still leak at points of weakness as they are simply under pressure; the product inside (Ammonia) is doing everything in its power to get out. They are also constantly moving, expanding and contracting, which is why it is paramount that your system is constantly assessed and maintained.
The crux of the matter is that, Ammonia should not leak. There is a misconception that because Ammonia is a natural refrigerant, it is ok to have constant "minor" leaks within an engine-room. It does not justify letting the product escape, small leaks have the potential to escalate, and escalate rapidly. If a leak has occurred - there is a reason why and it must be resolved as soon as practically possible. It may need re-torquing, replacing, there may be other forces at play such as vibration or it may be that the component has not been selected properly, installed misaligned or maybe it has a factory flaw.
There is also a cost benefit involved, Ammonia is cheaper than its ugly man-made cousins but even a minuscule leak can add up: 1 gram per minute is 10kg per week. 520kg per annum and $5000 cost to replace it not including specialist technician’s involvement. This aspect alone warrants the issue of personal hand held devices for key staff as well as installation of Fixed gas detection in numerous areas of the plant; a network of sensors wrapped in a well designed architecture of logic that drive controls and alarms. Having access to real-time and historical Ammonia detection data will provide better visibility and piece of mind for your workers and a gauge of where your pressure equipment is positioned in terms mechanical integrity and not to mention a viable solution to the notification debate and thorough evidence based reporting.
What if the leak was outside at an unknown concentration? What if the weather conditions were different that a plume, big or small was able to surpass the boundary? I don't have the answers, that is above my pay grade. My recommendations is anything uncontrolled above an STEL must be reported, if it is external or unknown it must also be reported. I am totally open to discussion around this topic and invite your input.
In terms of reporting, I have included our internal incident investigation/report tool for download as well as an iauditor version to add to your batch of templates. Please feel free to make them your own. If you need any advice all things Ammonia or want to discuss this in private, please don’t hesitate to get in touch. firstname.lastname@example.org