Breathing Apparatus wearers should return to the BA entry control point:
- Before their low pressure warning device or whistle activates
- Before the pre-determined return time specified in the BA team briefing
- Where a BA team member displays symptoms likely to affect their welfare, such as a heat- related condition. See Heat related conditions
The only exceptions are in the event of a:
- Set malfunction
- BA wearer becoming trapped
- Situation where a BA wearer’s air supply has to be augmented
Air consumption rate tables should be used to provide a predicted exit time for BA wearers. However, the person responsible for the BA entry control point should be aware that BA wearers consume air at different rates.
Each wearer will consume air at a different rate. These differences will be determined by a number of factors including:
- Body mass
- Individual levels of fitness
- Work rate
- Tasks undertaken
- Environmental conditions
- Personal protective equipment in use
- Psychological stress
To maintain an accurate record of air consumption each BA wearer must read their own gauge, make their own calculations, and inform the BA team leader of the pressure at which they will need to start exiting the risk area.
BA team leaders should regularly update the BA entry control operative about the air consumption of the BA team.
Calculating turn-around pressure is a technique used for the monitoring of air consumption and is regarded as good operational practice whenever BA is worn. However, there are circumstances when the calculation of turn-around times and subsequent communication and agreement with the person responsible for the BA entry control point and the BA team leader, would be inappropriate. For example: where life saving actions are required by BA wearers and BA teams are committed into a risk area to perform a specific task and to withdraw. It is anticipated that under such circumstances, air consumption will not be for the working duration of a BA set cylinder. During all other circumstances where BA is worn, calculating a turn around pressure should be performed.
Calculating turn-around pressure
Where the use of a turn-around pressure might be appropriate, the following methods may be considered:
Method 1: Making progress
This is used for tasks such as making steady progress into a hazard area.
The wearer notes their gauge pressure as they book in with the BA entry control point and start up their BA set. They then calculate their turn-around pressure by dividing their full duration by two, then adding half the safety margin. This is a basic calculation but will ensure that, if they begin to exit when this pressure is reached, they will exit before their low pressure warning device or whistle activates. For example:
|Method 1 example: Making progress|
Entry pressure = 200 bar
Divide by two = 100 bar
Half safety margin (60÷2) = 30 bar
Add the two = 100+30Turn-around pressure = 130 bar
Method 2: Working at a location
This is a more accurate method and can be used when a BA team enters a risk area and will be working for some time.
For example, if team 1 were sent into a risk area to relieve team 2, they would need to calculate the initial turn-around pressure on entry and take gauge readings regularly along the route. Once team 1 reached team 2, they would take another reading and calculate the pressure they had used to reach that point. Team 1 can then safely stay with the branch until the pressure drops to the point where they have sufficient air to exit back along the same route without entering their safety margin.
|Method 2 example: Working at a location|
Entry pressure = 200 bar
Gauge reading on reaching objective = 160 bar
Air used to reach objective = 40 bar
Air required to exit = 40 bar + safety margin (i.e. 60 bar)
Turn-around pressure = 100 bar
When using Method 2, the BA team will have more time to complete a task. This can make fire and rescue operations more effective and may mean that fewer BA wearers will be required.