The IAS cluster isn’t the issue here, the smoke sensor is supported by the device handler as per the specs. The group feature isn’t supported by SmartThings but if Frient wants they can add support for triggering the alarm on demand (via a custom device handler) which will allow you to then trigger the alarm using the Automation tool.
There are other sirens which can used with the Automation tool to trigger them if a smoke sensor is detected.
Many smoke sensor manufacturers in both the US and the UK do not allow third party automation control of the siren feature. In some jurisdictions this is limited by code. The concern is that people would trigger the siren for non-smoke events, including burglar alarms, and that would cause people to stop reacting to smoke alarms like smoke alarms.
Smoke alarms have a unique sound in the UK, Europe, the US, and many other countries because they are intended to signal to anyone who hears them that there is a fire and they should be prepared to evacuate. That’s not the response to a burglar alarm, where you may want the people to stay put to avoid running into the burglars.
For example, nest does not allow third-party triggering of their sirens on the nest protects. And none of the smoke sensors that have IFTTT services allow you to trigger their alarms.
Note that that’s different than causing the sirens to trigger each other, which is why there may be a way to do that on some platforms. But most manufacturers don’t want you to just set up a rule on your own. And it may not be legal in some jurisdictions.
So to be honest, I’d be surprised if any smoke sensor manufacturer advised “just set up an automation“ to make the smoke sensor siren go off.
It may be capability.siren , but it’s a special kind of siren with a legally defined acoustic pattern which is different from other sirens.
FWIW
Ok. So i can throw this back to Frient correctly and ask the right questions. They have told me its an IAS issue and that it can work on other hubs. They said their alarms do support it an will work but its hib specific. So IAS and group feature are different things? Both of which not supported by ST hub?.
I dont want to be fobbed off with wrong answers so i want to make sure i ask them and tell them the issue as it stands
I will certainly ask about a custom device handler but im not convinced they will change it.
Sorry your going to regret getting involved 
Im not a developer or programmer or anything so its not all 100% clear to me sorry
IAS just means it’s a zigbee Device that accepts a specific set of security system commands. IAS stands for “intruder alert system“ but it means both security and fire.
Anyway, I would keep it super simple. I would just describe what you want from a typical customer’s point of view: you want to set it up so that when one siren goes off your other sirens go off and you are using smartthings as your hub.
If they tell you there’s no way to do that, ask them if they know of another brand which does. 
I agree. I cant see them changing it or allowing automations to trigger them because of the risk of false triggers etc as you say. To be clear - they have not said this is the solution. They said its an IAS issue which is what I want to understand.
What confuses me is Why release a “supported by SmartThings” product when it doesn’t support full features. The only feature i can see it supports is a notification. Seems pointless
Current UK regs dictate the volume and distances required between fire alarms in domestic settings.
Have these Fire Alarms been given any official approval?
Stand alone they would not suffice and would need a wired alarm.
I have asked them that from the offset. They said its a hub issue and I need to speak to ST for help
I will speak to Amazon and get them sent back. I cant see how they are a good device now i have learnt their limitations. Id be better investing in something else.
Do you know a brand that does?
I don’t know what currently integrates with smartthings in the UK, if you print a screenshot of the available devices I might know. Use the +, then Devices, by device type, then smoke/fire.
Well here is the list
As you know i took the Frient route.
I could go through all of these and potentially find the same issue
FireAngel has interlink capability for both the Mains a Powered and Their Battery Powered smoke sensors. I don’t know how well they work with smartthings, though.
You might need to contact them to find out which models work with smartthings.
It looks like the popp smoke zwave Sensor also has interlink capability.
They also have an interesting option where they do allow you to create an automation for the siren, but if you use that then it will have a different siren sound then the legally defined smoke sensor sound.
Again, I don’t know exactly what options you get with the integration, but since Aeotec now owns popp, that seems promising
No device in the ST environment has full features support. It is not just about Frient. But you should read the fine print before buying.
If you need an interconnected fire alarm, go with the Nest ones, they do connect to your WiFi and they do have a bluetooth/thread connection between themselves as well. It is not supported by SmartThings but they are definitely certified and has a long history. They send message when triggered, and they do trigger each other if one triggered.
I have looked at Nest but wanted to stay with ST compatibility. I could be wrong but isnt it due to come? The only place Nest falls down is they dont offer a heat alarm which is required in a kitchen
Thanks for the lesson but the small print doesnt say. There is an asterisk that says *not all features are supported on all hubs
I asked Frient and they said its a case of checking with hub platform provider and I quote “we have removed the information about interconnectivity”
So yes maybe I could have asked ST the question for them to list every feature on every supported fire alarm listing the ones that dont work fully and the reasons why - but be honest, have you done that with the every product you have purchased?
The fine print translates to English as, NOT ALL features are supported on ALL hubs.
But you must know it better and SmartThings and Frient will implement all features prioritized for you. Just keep your finger on the pulse! You must be good in that!
I think we’ve all been frustrated at one time or another by finding out that some individual device had features that were not supported in an ST implementation. Even ones like Ring and Arlo with officially announced integrations. Or what seemed like basic vanilla zwave and zigbee.
Most hubs have a list of officially compatible devices, sometimes a pretty short list, making buying decisions for new devices pretty simple.
From the beginning, ST has had a much more open system but also added its own abstraction layer and the end result was never knowing for sure what will work unless you come to the forum and ask about a specific model. And even then the answers can change over time as the abstraction layer changes. (See Harmony, for example. Or Fibaro.)
It can be incredibly frustrating. Many manufacturers have given up trying to keep up with ST idiosyncrasies (again, see Fibaro). They certify to the independent third party standard and leave it at that. Others put a lot of time and effort into ST support (Zooz and Inovelli fall into this group, but don’t manufacture for the UK).
It’s a trade-off for the individual customer: a lot more devices to choose from, but a lot more work to figure out exactly which features are supported for any one model. 
Hi again.
Ive not been getting a straight reply from either ST or Frient and I want to be 100% sure im asking the correct thing.
So to simplify it I just need a yes or no answer to the first few question and then a little detail after to explain without being complicated please .
I know you have mentioned grouping and the siren option but that is not an option. Frient keep saying its an IAS issue.
So
Sorry to be quite direct but ive had so many different people say so many things im confused myself now.
Also ive sent some emails and IMs to the other companies supporting ST fire alarms. Not had a response from one of them 
Thanks in advance
IAS means Intruder Alert System. It is just a device class definition for Zigbee: almost all motion sensors, for example, identify themselves as IAS devices whether they are used for security or lighting control.
IAS has a whole list of “clusters,” which is the Zigbee term for the physical format of its messages. For example, a Zigbee contact sensor used with SmartThings would use specific IAS clusters to join the network, report battery level, report the sensor open, and report the sensor closed.
In this sense, of course SmartThings “supports IAS.” Many of the smartthings-branded devices were IAS devices. And the hub is a certified Zigbee 3.0 coordinator, which requires that it support a minimum set of IAS clusters.
But that’s like asking if a hotel restaurant has a bakery. It tells you something, but not enough. It means they probably bake their own bread. They probably do simple birthday cakes. It doesn’t tell you whether they do wedding cakes or doughnuts or tortillas, which are all specialty items.
In this case, SmartThings supports the basic functions of most individual IAS devices.
But what you want is group triggering. I don’t know exactly how frient does that, it might be through Zigbee groups, it might be through zigbee scenes. But either of those move us into wedding cake territory, and The last time I checked they are not functionality which was supported on the smartthings platform.
The following is from Tizen documentation, but it happens to have a really good basic definition of the IAS zone clusters for Zigbee. So don’t go clicking around in this document or you might get confused. I just want to give you this one page. And specifically I want you to notice that none of the commands on this page would cause one smoke alarm to trigger another, or let you treat them as a group.
So…does SmartThings “support IAS?” Sure, in the sense that you can add an individual sensor to a SmartThings setup and you should be able to write an automation that will respond to that sensor’s alarm one and alarm two (as defined in the IAS specifications).
But that doesn’t solve your use case of wanting one smoke sensor to trigger another.
I know this stuff is really technical, but that’s why I suggested that you focus your questions on the use case, not on the technical aspects.
It’s yes to the first question. The second question is kind of meaningless in this context, but I don’t want to go into all the details of why. It’s yes to the third question, but you have to define “used with.“ Can you take a single Frient smoke sensor, add it to a smartthings hub, and then recognize that it has sent out an alarm? Probably yes, although I don’t know if it would require custom code or if there’s anything else proprietary or tricky about it. But you can’t get one to trigger another, which is what you said you wanted to do. So bakery yes, wedding cake no.
If you want to get technical you can ask Frient what the fingerprint of its devices are, that is what specific clusters it advertises itself as supporting when it joins a network, then that would tell us more. But just being an IAS zone device doesn’t tell us much in this context.
I am both informed and hungry now, thanks @JDRoberts! 
I figured you’d appreciate that the best stripped down zigbee cluster definition I could find was in the Tizen docs. LOL! 
Ive reached out to Frient. I sent them an image of their user manual which stated that this was entirely possible - hence the reason i got them
They have advised me that they have since removed that option and the wording from their new user manuals.
I sent them back.
Basically they are now only capable of sending me a notification.
I am still hunting for a fire alarm that can give me wedding cake capabilities. Seems during
Covid everyones tech support is super slow or non existent.
