Multi-Unit Evac (Hybrid working)

Hi, 

I work on a multi-unit site, all relative close to each other.  Mix of offices and workshops. We evacuate per unit or "Zone", as required. We have Fire Marshalls (FM) in each unit or zone, and perform a sweep and roll call system.  We have a hybrid working policy. FMs are often moving around site for meetings etc.

Increasingly we are seeing issues guaranteeing availability of Fire Marshalls (FM) in each unit in a hybrid working context. We can't monitor their availability, and our alarms aren't linked across units. 

Wondering if anyone could offer some intuitive ideas to manage this? I was thinking of the following in terms of mitigation;

• Hand-held radio in each unit (i.e. stored in a FM box which is collected by last person out). 
• Additional radios issued to each FM (for them to hold at all times).
• That gives a means of communication between staff and any available Marshalls for support, should their unit be short of an FM. 

In terms of actually preventing the lack of FM availability, I'm less sure how to tackle it.