Trust all my readers are safe and doing well. Slowly but steadily we all are recovering but the threat of the pandemic has not vanished. We need to be careful and not let our guard down at any cost. This blog is a conclusion of the complete firefighter. In the first part we had basically dressed up the firefighter for facing the Hazardous condition called Elevated Temperature. Here we shall equip him to deal with Oxygen deficiency and Smoke Conditions. In some places the firefighters are called to rescue persons trapped in confined spaces. Without further ado let us get started.
In any fire ground operation when the fire is in the Fully Developed or Fully Involved stage it is very deadly. The heat and smoke emitted from the fire has often taken the lives of firemen and the threat of back draft is ever present. Any human has to breathe air to live and a fireman too needs to breathe if he has to bring the fire under control. But in fire ground operations there is always a thick blanket of smoke that makes breathing next to impossible and the noxious gases like Carbon monoxide, Hydrogen Cyanide and a lot of other gases which can kill within minutes. A firefighter needs a device which can help him breathe and help him to fight the fire. That apparatus is called SCBA. Self Contained Breathing Apparatus. The SCBA helps the firefighter to breathe air so that he can breathe easy and still do his job of firefighting and Rescue. Let us see how the apparatus is made and how it works.
A SCBA typically has 3 main components,
1. A cylinder under pressure
2. A pressure regulator
3. Inhalation connection
All connected together and mounted on a back plate with harness and straps.
The Cylinder: The cylinder is made of either Steel, Aluminium or Carbon composite (Carbon fibre) material. Initially the cylinders were made of steel as it was durable and could withstand high pressure, but they were heavy and impeded movement. With the advances in technology now the material is Carbon Composite and considerably lighter. The pressure ranges from 2,216 to 5,500 psi or 154 to 376 atmospheres (BAR). The cylinder is filled with breathable air and to the neck of the cylinder is fitted a valve to open and release the air for breathing. The cylinders comes in various sizes like 4ltrs, 6ltrs and 6.8ltrs. The modern fire fighters mostly use 6ltr or 6.8ltrs. The cylinders have to tested hydrostatically once in 5 years. These cylinders are commonly called air bottles.
Pressure Regulator or Demand Valve: The demand valve supplies air to the wearer on demand. It has a bypass facility and a reset button. The demand valve is connected to the facemask through bayonet fitting. A reducer reduces the pressure from 300 BAR to 6 – 11 BAR. It will also have a pressure gauge to indicate the pressure and will have an alarm whistle to indicate to the wearer that the air is getting exhausted. Hence a trained firefighter will not use the air in the cylinder unless necessary.
Inhalation Connection: The modern breathing apparatus have a full face polycarbonate mask to which the demand valve is connected to help the firefighter breathe easy. It contains an inner mask and head straps.
There are 2 different types of SCBA which are positive pressure and negative pressure, but modern firefighters use positive pressure only. The air in the apparatus can last only for a certain amount of time and the calculation of time is as under.
The above calculations are as per standard formula and will vary from individual users and conditions.
Breathing through an SCBA is not as easy as breathing normally. Hence the wearer needs to be physically, medically and mentally fit. Usually the firefighters need to wear the fire suit and SCBA while practicing and during drills.
The wearing of an SCBA is called Donning and some of the donning methods are.
- Over the head.
- Coat Method.
- Seat mounted method.
The only problem faced by firefighters while wearing it they cannot communicate effectively. Hence firefighters design specific signals to communicate.
When the firefighter is dressed in fireman suit and he has the breathing apparatus with him then he is complete in all respects and can save numerous lives. Trust this article of mine will underline the importance of protecting our firefighters.
The Fire and Rescue Services Act says that a Fire suit and SCBA are compulsory in organizations which have the internal fire hydrant system so that the trained people can fight the fire safely till the time the firefighters arrive. What is a Fire hydrant and how it is used in firefighting we shall discuss in the subsequent blogs.
For technical specifications of SCBA, visit www.ushafire.com and www.resguardo.com
Till then stay safe and be safe.
Seshadri Varadarajan.