An engineer checking a pump below the production floor can be just metres from colleagues and still be unable to call for help. The same can happen to a technician in a shielded test room or a cleaner at the far end of a warehouse.
Protecting lone workers in dead zones starts with finding out where alerts fail, then making sure there is a tested way to raise the alarm and get help to the worker.
What Is a Dead Zone on an Industrial Site?
A dead zone is an area where the network a device relies on is unavailable or too unreliable to carry a call or an alert. Basements, thick concrete walls, metal structures and shielded rooms can interrupt mobile or Wi-Fi coverage. For example, a phone might work at the entrance but lose signal as soon as the worker goes downstairs or closes a door.
Even if there’s no mobile signal, a site radio or a dedicated wireless network may still work. The key is to test it where people actually work.
Map Dead Zones Along Real Working Routes
Start with tasks that take people away from their teams: checking a pump in a basement, inspecting equipment in a separate building or cleaning a production area after the shift ends. Include contractors too, and look at the routes people take between jobs as well as the places where they stop.
As you walk those routes, test the equipment workers carry, with doors shut and the site operating normally. Send a test alarm from each work area, including behind machinery and on different levels. Then check that the person on duty receives it and knows where to go.
Once you’ve found the gaps, mark them on the site plan using the building, floor, room or equipment names your team already uses. That way, when an alert comes through, responders can match the location to a place they recognise.
Give the Alarm a Route Out of the Dead Zone
Detecting an incident, sending an alert and locating the worker are three separate functions. For example, a fall sensor might trigger a local alarm or store a message until the device reconnects. If nobody receives the alert at the time, the worker may still be left waiting for help. What you do next depends on which connections are available in that area.
| What the site test shows | What to consider |
|---|---|
| One mobile network drops out but another works | A device that can use multiple mobile networks. Test which networks it can actually access at that location. |
| The worker has no mobile signal but can reach a site network | An alarm that uses the available Wi-Fi or radio network, with a test of the full route to the responder. |
| Mobile and Wi-Fi are both unreliable in the work area | An engineered alternative, such as a dedicated LoRaWAN network or a fixed emergency call point, depending on the task and whether the worker could reach it. |
Bear in mind that an SMS fallback still needs a usable connection. If a device has to wait until it reconnects, the alert will be delayed too.
How LoRaWAN Can Carry Alerts Without Mobile or Wi-Fi Coverage
When neither mobile nor Wi-Fi coverage is reliable, LoRaWAN is one option to consider. It’s a low-power wireless technology that allows compatible devices to send short messages to a gateway. The gateway forwards them to the network and application that handle the alert. The wearable does not need mobile or Wi-Fi coverage at the worker’s location if it can reach the LoRaWAN gateway and the onward connection is working. LoRa Alliance overview of LoRaWAN.
Plan What Happens If Contact Is Lost
Alongside alarm coverage, plan for what happens if contact is lost. Where the risk assessment allows lone working, agree who is expecting the worker back, when they should check in and what to do if they miss that deadline. Set the interval based on the task and how quickly help may be needed. After all, a missed check-in tells you contact is overdue, but it doesn’t tell you when an incident happened.
To make that plan work, give the person on duty the worker’s task, exact location and safe access route. Name a backup and rehearse what to do if a check-in is missed, so nobody is sent into an unsafe area. HSE’s lone working guidance calls for regular testing of monitoring systems and emergency procedures.
Depending on the task, you may also need additional people or specialist rescue arrangements. For example, if confined space entry is unavoidable, suitable emergency arrangements need to be in place before work starts. A working alarm does not replace them.
How to protect Lone Workers When There’s No Signal
As seen, a dead zone can delay help after an injury or sudden illness. That’s why it’s worth mapping the gaps, testing how an alert gets through and rehearsing the response together.
For the worker, it comes down to this: the alert needs to reach someone who knows where to go and can get help there in time.
Yes, if it can send alerts over another working connection, such as a site Wi-Fi or LoRaWAN network. With LoRaWAN, the device needs to reach a gateway, and the gateway needs a working connection to forward the alert to the monitoring system.
Try a test alert using the device workers actually carry, from the places where they work, including basements and shielded rooms. Test under normal working conditions, with doors closed where relevant. Confirm that the person on duty receives the alert and can identify the correct building, floor.
