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Analysis of combustion test method for UL94 HBF HF-1 HF-2 foam

Foamed materials burning test method analysis, UL94HBFHF-1HF-2 horizontal combustion test; corresponding regulations: UL94; CNAS approved project; applicable products: foam material; sample size: 15pieces (150 + 5) X (50; sample pretreatment: 1. sample should be placed before the test temperature 23 + 2 C, relative humidity 5; 2. samples before the test should be placed at the temperature 70 70 1 degrees of air circulation box; test method: UL9 4: 1997, astmd4986; test related introduction: in the test piece of 25 mm, 60 m UL94 HbF HF-1 HF-2 level combustion test.

Sample pretreatment:
1. Before the test, the sample should be placed in the environment with temperature of 23 ± 2 ℃ and relative humidity of 50 ± 5% for at least 48h
2. Before the test, the sample should be placed in the air circulation box with the temperature of 70 ± 1 ℃ for at least 168h, and then cooled in the dryer for at least 4H at room temperature
Test method:
UL94:1997, ASTM D4986-03 (foam plastics), IEC 60695-11-10 (2003), ISO 3852-88 (soft foam material);
Test related introduction:
At the 25MM, 60MM, 120MM of the specimen, a reference mark is made. The flame of the wing top nozzle is applied to the side of the foam plastic placed horizontally on the screen, and the ignition time is 60S, and the burning rate of the specimen is measured.
UL 94 HBF：
The burning rate of the material between the two marks of 25 mm and 125 mm shall not exceed 40 mm / min, or the material shall self extinguish before the mark of 125 mm, but it does not meet the requirements of UL 94 HF-1 and UL 94 HF-2;
UL 94 HF-1：
At least four of the five specimens in a group have an open burning time less than or equal to 2S, and the open burning time of any one specimen is not more than 10s. After 60mm marking, the sample failed to break. After the ignition source is removed, or after 60mm marking, the burning time of the specimen is not more than 30s, and there is no droplet;
UL 94 HF-2：
At least four of the five specimens in a group have an open burning time less than or equal to 2S, and the open burning time of any one specimen is not more than 10s. After 60mm marking, the sample failed to break. After the ignition source is removed, or after 60mm marking, the burning time of the specimen is not more than 30s, and the droplet ignites the absorbent cotton.
UL94 has 12 fire grades:
HB， V-0，V-1，V-2， 5VA，5VB，VTM-0，VTM-1，VTM-2，HBF，HF1，HF2。 Hb, V-0, V-1, V-2, 5VA, 5vb are suitable for general hard plastics, vtm-0, vtm-1, vtm-2 are suitable for plastic film, and wire HbF, hf1, hf2 are suitable for foaming materials.

Introduction to NEBS certification
NEBS is the English abbreviation of "network equipment – building system". Its origin can be traced back to the 1970s. Bell Labs, the giant of the U.S. telecommunications industry, developed a complete set of documents detailing a regional Bell operation company, The standard environment of the main engine room, including the description of the room space and environment.
Bell laboratory's original intention of developing this document is to help equipment suppliers understand the environmental requirements of the computer room, design equipment that meets the requirements at a lower cost, and reduce the entry threshold of equipment suppliers. Two kinds of files commonly used for testing include:
-Gr-63-core-network equipment construction system requirements: physical protection
-Gr-1089-core - Electromagnetic compatibility and electrical safety - general network communication equipment standard
The former standardizes the part of physical protection, including the most basic space and environmental standards
Environmental requirements include:
·Temperature and humidity
·Fire prevention
·Equipment management
·Earthquake
·The vibration of machine room and transportation process
·Air pollution
·Noise
·Lighting
Requirements of the site part:
·Cable distribution systems
·Distributing and interconnecting frames
·Power equipment
·Operations support systems
·Cable entrance facilities
Gr-1089-core mainly regulates the requirements of electromagnetic compatibility (EMC) and safety, including:
·Electromagnetic interference (EMI)
·Electrostatic discharge (ESD)
·Lighting
·AC power interruption
·Static energy sensing
·DC potential difference
·Electrical safety
·Corrosion
·Connection and grounding
Gr-78-core is the first of other important documents, which provides a guide for product design and manufacturing, and is very worthy of reference. Relevant information can be obtained from Telcordia's official website.
Classification of NEBS
NEBS has a rigorous grading system, which is divided into three levels according to the possible impact on application functions and network performance.
"NEBS level 1" is applicable to the situation that has the least impact on the safety of personnel and equipment and the network performance. Level 1 does not emphasize operability. Generally, level 1 is only required for prototypes entering the site for trial or network equipment used by regional telecom service providers (CLEC) to connect to RBOC
"NEBS Level 2" emphasizes the operability in a specific environment. Because the so-called "controlled" environment needs to be clearly defined, level 2 is less common.
"NEBS Level 3" is also the highest level that can be recognized at present, which can also be said to be carrier class. All the standards of gr-63-core and gr-1089-core should be fully complied with.
EN779
The new European standard for air filters (en779:2012) came into effect in 2012. Its purpose is to classify air filters according to their minimum filtration efficiency, which is also called me (minimum efficiency). The new standard is a welcome move and a step towards a better indoor environment.
The new standard will help to eliminate some problems. One of them is a chemical fiber filter with static electricity. Although these filters show good initial filtration efficiency, their static electricity disappears very quickly, which makes the air filter's ability of purifying air decrease sharply.

Unfortunately, one of the results of the above situation is that a very large number of European companies now use F7 filters with minimum efficiency between 5% and 10%. This means that up to 90% to 95% of the pollutants in the outdoor air can enter buildings and pollute the indoor environment.

Based on the classification of minimum efficiency, the new standard will force these filters out of the market. At the same time, it will help to develop chemical fiber filter materials with better dust filtration performance. Unfortunately, that will come at a price - higher resistance and more energy consumption.

Not all primary filters are the same - even at the same level!

The problem with the new classification is that although the worst filters will disappear from the market, there is room for the good filters to become worse. Although energy conservation can be achieved through the lowest possible resistance, such development may be regressive. For example, for 0.4 μ m dust particles, our (F7 level) minimum filtration efficiency is 54%. However, for filters classified as F7, the standard requirement is not less than 35%.

As we have made it clear, we will not reduce the efficiency of our filters. This will cause about 40% of the air quality to deteriorate. But the risk is that other manufacturers may not do the same. Instead, they may see opportunities in standards to reduce resistance and thus energy consumption. This will lead to worse air quality.

The problem with the new classification is that although the worst filters will disappear from the market, there is room for the good filters to become worse. Although energy conservation can be achieved through the lowest possible resistance, such development may be regressive. For example, for 0.4 μ m dust particles, our (F7 level) minimum filtration efficiency is 54%. However, for filters classified as F7, the standard requirement is not less than 35%.

As we have made it clear, we will not reduce the efficiency of our filters. This will cause about 40% of the air quality to deteriorate. But the risk is that other manufacturers may not do the same. Instead, they may see opportunities in standards to reduce resistance and thus energy consumption. This will lead to worse air quality.

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