Positive Pressure Air Respirator Low Pressure Alarm Technology Analysis

Positive-pressure air respirator is one of the most important fire-fighting equipment for fire protection officers and soldiers. It is extremely important to use fire-fighting positive-pressure air respirator correctly in the fire fighting operations of the fire brigade. It is directly related to the life safety of combat officers and soldiers. This article will focus on the key parts of the air breathing apparatus - the use of low-pressure alarm device performance and alarm technology for analysis, for the grass-roots fire-fighting force the correct selection of positive pressure air breathing apparatus reference.

Positive pressure air respirator consists of a back frame, a gas cylinder, a cylinder valve, a pressure reducer, a safety valve, a low pressure alarm device, a pressure display device, an air supply valve, a mask, and the like. After the cylinder valve is opened, the compressed air in the cylinder is decompressed by the pressure reducer and sent into the air supply valve through the medium pressure conduit. When the firefighter needs to breathe, the air supply valve supplies air to the mask, so that the firefighters can maintain normal breathing. . However, the compressed air inside the cylinder is limited, and the time of use depends on the volume of the cylinder. When the compressed air in the cylinder is about to be used up, the pressure in the cylinder consumes about 5.5 MPa, which means that the cylinder can be used for breathing. There is not much left in the air, and the alarm device must remind the firefighters to immediately evacuate the dangerous scene. Otherwise, the life safety of the firefighters may be endangered due to insufficient air supply. At present, most of the air-breathing fire fighting units use high-decibel sounds to warn of inadequate cylinders. In recent years, new products such as electronic acousto-optic alarms, vibration-assisted alarms, and intelligent control alarms have been introduced on the domestic market and gradually accepted by the firefighting forces.

A high-decibel sound alarm

That is, when the pressure in the cylinder drops to 5.5 MPa, a low-pressure alarm device is triggered and the alarm whistle opens. The airflow in the compressed air generates a sound of no less than 90 decibels through the alarm whistle to remind the firefighters to evacuate the site.

Disadvantages: alarm whistle placed behind the air respirator, called the rear alarm air respirator, rear-mounted alarm air respirator is very easy to cause neglect or misunderstanding in the high-temperature complex fire environment, the current method of air respirator alarm The use has gradually decreased. The alarm whistle and the pressure display device are hung together in front of the chest. This is called a front-alarm whistle air respirator. This kind of front-mounted whistle alarm is a more traditional method of use in the military and is used for a long time. It is widely used throughout the country. One, many grassroots units are still in use. However, the front-mounted alarm whistle is not easy to hear due to external environment interference in a noisy place.

Second, vibration auxiliary alarm

Extinguishing and Rescue Firefighters on-site are noisy in the environment and may not be aware of the sound generated by insufficient gas sources, which may affect the timely and safe retreat of firefighters. To this end, in recent years, the domestic market has introduced an air breathing apparatus with vibration assisted alarm function, which is to add an additional alarm function to the vibration of the supply valve on the original equipment. When the cylinder pressure reaches a certain set value, the alarm Whistle and vibration start the alarm at the same time. The vibration alarm is to use the air flow to push the small piston to oscillate in the air supply valve. The vibration wave is transmitted to the firefighter's face through the air supply valve and the mask, so that the user can send an alarm to the air caller he is wearing. Accurately and directly determine the purpose. At the same time, it generates high-band whistle and vibration sound, which causes firefighters to pay attention and evacuate the dangerous scene as soon as possible. The air breathing apparatus directly uses the human body's tactile sensation to directly sense the alarm issued by the air breathing apparatus, and prevents the user from quickly taking corresponding emergency measures because it is difficult to discern the source of the alarm when the traditional air caller alarm whistle sends an alarm sound. The way for the user to accept the alarm only relies on the auditory promotion to the double reminder of hearing and touch, thus greatly improving the timeliness and effectiveness of the alarm mode.

Disadvantages: First, it is necessary to consume air breathing apparatus. This kind of air respirator's vibration power comes from the high-pressure air for firefighters to breathe. The high-pressure air flow restricts the flow and then pushes the small piston installed in the air supply valve to make the small piston hit back and forth, thereby generating oscillations and sounds. The process will consume some high-pressure air. In this state, the air consumed by firefighters is consumed. In this way, the escape time of firefighters after the alarm will be shortened slightly, and the exchange of firefighters will be reminded of the firefighters' insurance. Second, the country does not have a vibration-assisted alarm pressure standard. The national standard for sound alarms starts the alarm when the cylinder pressure is reduced to 5.5 MPa. It is recommended that the vibration-assisted alarm cylinder pressure be set to 7 MPa when the alarm is activated, because the vibration-assisted alarm needs more Gas source.

Third, intelligent control alarm

With the development of modern electronic technology and wireless technology, air breathing apparatus equipped with electronic technology has also been put into actual combat. The so-called electronic air breathing apparatus uses electronic devices to control the alarms such as light emission and vocalization. Some of these air breathing apparatus have added electronic display and alarm devices separately, and some have been equipped with radio communication systems. Air respirator with electronic display and alarm is equipped with an electronic pressure sensor at the pressure output to convert the pressure parameter change into a current parameter signal, and then emit light, sound or vibration through various electronic components to remind firefighters. Understand the state of your equipment. When the firefighters hold the alarm for a short period of time or manually trigger an alarm, the alarm system will emit a sound with a middile decibel. When it is a little longer, a high-decibel alarm will sound and the indicator light flashes. Firefighters or rescuers send out sound and light signals to indicate the wearer's and his air respirator's movement status or position so that they can be rescued in time. If at this time, the wearer moves slightly, the alarm can be eliminated. If you continue to hold for about 10 seconds, the system will enter the full alarm state. At this time, a high-decibel alarm will sound directly, and the indicator will flash. When the pressure of the air respirator cylinder is full or when it is used down to the original 1/2, 1/4 or other pressure value, the light-emitting diodes will emit different colors of sparkling light to remind the firefighters of their own state of the equipment. When the bottle pressure drops to about 5.5MPa, the LED will emit a red sparkle and light, and an alarm system such as sound and light will be activated to prompt firefighters to evacuate the dangerous scene. Such air respirator is generally equipped with a HUD (Head Up Display) system in the mask.

Disadvantages: First, the limitations of the use environment such as temperature. The electronic air breathing apparatus is realized by a combination of electronic components and some mechanical devices, and the power of the electronic components comes from a dry (accumulator) battery. The use of the electronic device is limited to the specified temperature limit due to the limitation of the use range of the temperature of the battery. Some batteries will reduce the power, and some may even completely lose power. The second is the use of unstable performance. Also in the extreme temperature environment, some electronic components may have various instable state defects, so the application range of the electronic air breathing apparatus in terms of temperature and the like will be lower than that of commonly used electronic air respirator.

Fourth, monitoring command and alarm

That is, an electronic air breathing apparatus equipped with a radio communication system in contact with a commander, also called a monitoring command system. This system is equipped with a wireless communication system in addition to the above-mentioned functions of the electronic air breathing apparatus. When the firefighter air respirator is low-pressure alarm, the rear base station will also display the same information, with front and rear simultaneous alarm function. The air breathing apparatus is a system of 6-12 with an emergency event management system. The emergency event management system is an integral part of the complete system. It includes personnel deployment and radio communication functions. Commanders can use it to grasp the status and important information of all firefighters and air breathing apparatus worn in real time, which greatly improves on-site command. The effectiveness and safety of firefighters. The system can be alerted through two-way, wireless, non-verbal communication and acousto-optic methods. Firefighters can automatically or manually issue a call for rescue and evacuation request signals. Commanders can respond quickly, issue orders, and send search and rescue forces in a timely manner. . At the same time, in an emergency situation, the command platform can also actively call the firefighters' terminal and issue evacuation requests according to the conditions at the scene to achieve two-way wireless remote monitoring.

Disadvantages: First, after the firefighting force arrives at the scene, the monitoring and commanding alarm system needs to draw an electronic topographic map first. Usually, the scene of firefighting and rescue is rather chaotic and it is difficult to accurately draw the scene map; secondly, the distance of the system signal propagation is greatly affected by the site environment and it is far from the wireless launch. The farther the device is, the weaker the signal is, and the wireless signal is difficult to be guaranteed in a full-metal complex environment such as a cabin. Third, the air respirator of this function will also cost much more than the general air respirator, and the use cost will be relatively low. high.

In summary, with the development of modern science and technology, air breathing apparatus is also constantly developing and innovating. The low pressure alarm function of air breathing apparatus is from a single sound alarm, sound and vibration alarm to sound and light combination or acousto-optic plus vibration. The combination of alarms, from the no-use status display to the use of the HUD display, provides the firefighting force with more options. Although there is plenty of room for us to choose, from the analysis of the low-pressure alarm technology in this paper, there are also a large number of immature and unstable air breathing apparatus on the market. Grass-roots fire-fighting forces should choose their own air respirator according to different technical requirements in order to provide better protection for the fire brigade officers in their fire-fighting and rescue operations.