Do smoke alarms work?
First of all, a conclusion: smoke alarms are by far the cheapest, most convenient and most effective tool for saving fire damage. It can detect a fire early and alert the police, thus extinguishing the fire at the initial stage and avoiding the loss of life and property.
Here are some of the reasons
The law of fire development and the role of smoke alarms over time.
Indoor fires are divided into four stages: the initial stage of fire, the boom stage, the fully developed stage, the exhaustion stage
Early stage of fire: the burning area is small, the intensity of combustion is weak, the temperature is not high, at this time if the fire can be found early, with simple tools can be broken.
The combustion stage: At this time, the temperature in the room basically rises to 400-600°C. All combustible materials in the room burn instantly and at the same time, and the fire basically kills anyone who enters. The fire is already difficult to control.
Fully developed stage: the temperature rises rapidly, the face base expands rapidly, the burning speed accelerates, ordinary civilian fire fighting equipment can not control the fire, professional 119 also have to pay a great price to be able to put out.
Decay stage: the reduction of combustible materials or the consumption of oxygen will slow down the rate of combustion know gradually extinguished, but there is still a risk of ignition and explosion.
The only way to minimise the damage is to detect the fire at its early stages and extinguish it quickly. Smoke alarms can detect a fire early and provide an audible and visual alarm to extinguish the fire as soon as possible, so they are undoubtedly a great tool for reducing fire losses.
Secondly, can smoke alarms really detect fires as early as possible?
Let’s look at the demonstration done by Hangzhou Fire
To recap.
At the 26th second of the fire, the smoke alarm in the same area sounded the alarm; in another room with an open door, the smoke alarm sounded the alarm at the 44th second. In another room with a closed door, the smoke alarm sounded ten minutes later.
In another experiment with an electric car fire, the alarm started at 24 seconds in the same space, 36 seconds in another room with an open door and 1 minute 18 seconds in a room with a closed door. (I won’t show the video here)
So we can clearly feel that smoke alarms can detect a fire in the shortest possible time and sound the alarm. However, it is also important to note that smoke alarms need to be placed in a reasonable layout to avoid delaying the alarm, which we will talk about below.
So, how do I buy a smoke alarm?
Third, the knowledge of smoke alarms
1, the classification of smoke alarms: ion and photoelectric type
Photoelectric sensing it is the use of the smoke generated when the fire can change the basic nature of the propagation characteristics of light and developed. According to the absorption and scattering effect of smoke particles on light. Photoelectric smoke detectors are divided into two types: shaded and diffused. The optical smoke detector has an optical labyrinth and is fitted with an infra-red counter tube. When there is no smoke, the infra-red receiver tube does not receive the infra-red light from the infra-red emitter tube, but if smoke enters the optical labyrinth, the smoke is refracted and reflected, the receiver tube receives the infra-red light and an intelligent alarm circuit determines whether the threshold value is exceeded.
The ion type smoke detector has an ionisation chamber, it has a radioactive source of americium 241 inside and outside the ionisation chamber, the ionisation produces positive and negative ions, each moving towards the positive and negative electrodes under the action of the electric field. Under normal conditions, the current and voltage in the inner and outer ionisation chamber are stable. Once a fume escapes the outer ionisation chamber and interferes with the normal movement of the charged particles, the current, voltage will change, destroying the balance between the inner and outer ionisation chambers, whereupon the wireless transmitter sends out a wireless alarm signal, notifying the receiving host at a distant location to pass on the alarm information.
The difference between the two, ion type is more sensitive to tiny smoke particles, while photoelectric is more sensitive to slightly larger smoke particles. Generally speaking, there are more tiny particles when the flame is large and more large smoke ions when it is smothered. When the fire is large from the start, ion smoke alarms will alarm earlier, although the difference in time interval is not much compared to photoelectric, but this type of fire spreads very quickly, so there is a possibility of such a fire in the premises with ion type. For other environments where smouldering fires are likely to occur, the photoelectric type is preferable.
Of course, if it’s an important place and you can’t tell what the environment is like, then it’s advisable to have both or to buy a combination.
It is also important to note that ion alarms contain radiation, which is within the safe range (I have seen people specifically measure that at a certain distance and with a barrier, the radiation emitted is no different from that of the environment in everyday life), but it depends on your sensitivity to decide whether or not to buy one of these.
However, after check it with Leiz International, I think we don’t need to tangle with it, now it’s basically a photoelectric type smoke alarm, I don’t see any ion type.
2, The classification of smoke alarms: single-point and interconnected
To put it simply, the single point is that you have a fire in this room, only the room alarm will sound, another room alarm does not detect the fire will not sound. If the alarm in another room does not detect a fire, it will not go off. The interconnected type means that if the alarm in this room goes off, the whole interconnected alarm will go off.
Generally speaking, there are more single-point alarms for families and more interconnected alarms for public places.
3, The smoke alarm basic functions and additional functions
Basic functions: In accordance with the relevant national standards act, smoke alarms should be alarmed at a range of 3m to 80 decibels, while there is a self-test function, low battery alarm function. Smoke alarms should have an insect screen and be equipped with a battery that can support a minimum of one year of power.
Cheap alarms will basically just have basic features, slightly more expensive alarms will have various additional features, including but not limited to.
1, About 10 years of power
2, Mobile phone alarm notification function
3, Network alarm function
4, Infrared night vision function
Fourth, smoke alarms recommended
At present, smoke alarms are not much technical content, buy more famous brands can be, such as flame warriors, Hyman, millet, Gonzales, green rice, etc., and then recognize the 3C certification, the other according to their desired function to choose.
First choice: Hyman
Reason for recommendation.
10 years battery life, free from the trouble of changing batteries, more than 80 decibels alarm sound, the sound is bigger, fire-resistant high-temperature materials, not easy to burn, indented dustproof design, reducing the trouble of cleaning.
The bad thing about this model is that it does not have a network alarm function.
How to change smoke detector battery?
With the gateway, can realize the mobile phone alarm APP push, can match 50 alarms for linkage alarm. It can be sent to 5 devices. It is more secure. The gateway is able to manage a range of about 100 square meters. Larger range linkages require more specialised equipment.
There is also a wifi-enabled Ling Defence
This is a common alarm, also 3C certified, but not as many features, it is a common product, you can choose this if you do not want to spend so much money.
There are also two types of flame warriors, the difference is not big, 1 year of 32, 10 years of about 80.
If you buy this model, it comes with 4 years of NB-LOT service, and you have to pay for it separately if it expires, the price is about a few dozen to over a hundred dollars a year. If you don’t have wifi in your home or are afraid that you won’t receive the alarm signal if the wifi is disconnected, this will be better.
There is a more expensive smoke detector with added visualisation, i.e. with a camera, so you can check the fire remotely when the alarm is on. But with cameras, you have to be careful not to turn them into live feeds.
For corporate purchases, institutions and other large spaces that require linked alarm devices, the following professional grade smoke alarms are generally used. Can a host drag up to 250 smoke alarms, with telephone, SMS, WeChat alarm function, alarm sound greater (110 decibels), able to achieve 3000 meters of long-distance transmission.
At present, smoke alarms are these types of products, you can buy according to their needs.
Five, smoke alarm installation and maintenance
1, the installation of smoke alarms.
Another thing to note is that
Do not install in a wet location, such as the bathroom
The kitchen is best not to install, if you want to install it from the top of the fire source position at least 1 meter above
Do not install in a location where there is an obstruction underneath, as this can easily block the smoke and cause it not to alarm.
Do not install in a draughty location, as this may prevent smoke from being absorbed and cause non-alarms
Generally there should be a smoke alarm within 10 metres. It is also advisable to have one in each space to avoid the situation of not being able to detect the smoke in time when the door is closed. According to their own family space to buy the number of purchases can be.
2, The maintenance of smoke alarms
Generally speaking smoke alarms are best self-tested once a month, some smoke alarms with a mobile phone app, you can directly through the mobile phone app to detect, if not, you have to climb up and down to detect.
It is also best to clean the dust once every six months to avoid false alarms.
That’s all there is to know about smoke alarms. If you value home safety, read this article, which also has professional answers.
