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Glossary

combustible gas
Generally, gas which ignites and burns in air or oxygen.
Gas or steam that produces an explosive atmosphere when mixed with air at a certain ratio.
Explosive range (combustion range)
Concentration range where flammable gas mixes with air and explodes on ignition.
It is the concentration between the upper limit of explosion and the lower limit of explosion.
Example: The explosion range of hydrogen is 4.0 vol% to 75 vol%
Explosion lower limit
The lowest concentration at which explosion occurs when a flammable gas and air mix and an ignition source is present.
Explosion upper limit
The highest concentration causing explosion when flammable gas and air mix and an ignition source is present.
LEL
Abbreviation for Lower Explosive Limit, translating it as the lower explosive limit.
The lowest concentration at which explosion occurs when a flammable gas and air mix and an ignition source is present.
Example: LEL of hydrogen is 4.0 vol%
UEL
Abbreviation for Upper Explosive Limit, translating as explosive upper limit.
The highest concentration causing explosion when flammable gas and air mix and an ignition source is present.
Example: UEL of hydrogen is 75 vol%
vol%
A gas concentration expressed in a ratio of 1/100.
ppm
Gas concentration expressed as a fraction of one million.
ppb
Gas concentration expressed in 1 part of 1 part.
in the air
In general, an atmosphere at a temperature of -10 to + 40 ° C at 1 atmosphere (1013 hPa) and a humidity of 95% RH or less.
Gas detection
Quantitative grasp of gas concentration.
Hazardous gas (hazardous gas)
Gases that have various deleterious effects such as irritation, corrosion, asphyxia, etc. in the living body.
In a broader sense, it may include oxygen deficient air.
Toxic gas (toxic gas)
Among harmful gases, gas with low tolerable concentration to human body and toxic.
Allowable concentration
Concentration at which it is judged that most workers are not adversely affected by health if workers are exposed to harmful substances and the concentration of harmful substances in air is below this value.
Recommended values from ACGIH and the Japan Society for Occupational Health are quoted frequently.
TLV
The ACGIH and the like of the United States recommend it as a concentration of harmful substances that most of workers are not expected to suffer health hazards even if repeatedly exposed daily.
In English it is called "Threshold Limit Values (TLVs)".
TLVs include "TLV-TWA", "TLV-STEL", and "TLV-C".
ACGIH
Abbreviation for American Conference of Governmental Industrial Hygienists.
In Japan, it is called "American Industrial Hygienist Expert Meeting".
We recommend admissible concentration values of harmful substances for each substance.
TLV-TWA
It is the time weighted average concentration of harmful substances that are considered not to suffer health hazards even when repeatedly exposed in the average work of 8 hours a day or 40 hours a week.
Abbreviation for English "Threshold Limit Value Time Weighted Average", translated as Japanese time-weighted mean exposure limit.
TLV-STEL
The concentration of hazardous substances that does not adversely affect health workers if the daily exposure is below TLV - TWA even if the worker is continuously exposed for 15 minutes.
Abbreviation for English "Threshold Limit Value Short Term Exposure Limit", translated as short exposure limit value in Japanese.
TLV-C
The concentration of hazardous substances that should not be exceeded instantaneously during work.
Abbreviation for English "Threshold Limit Value Ceiling", translated in Japanese as exposure upper limit or ceiling value.
Gas anniversary (October 31)(In Japan)
In Japan it is said that gas lamps were first lighted in Yokohama on October 31, 1872 (Meiji 5).
In the Showa 47 years after that, as the beginning of the city gas business, the Japan Gas Association set this day as "anniversary of gas."
First gas lamp in Japan
In 1872 (Meiji 5), a gas company was lit up by a gas company of Takashima Kayonemon across Yokohama's coach road and Honcho street.
This is said to be the first gas lamp in Japan.