As firefighter and emergency responders have to play different role in line of duty. Apart from firefighting, firefighter need to respond to other emergencies which are more critical in term of the job performance and used to require calculated, conscious and in depth approach.
Hazardous material incidence calls are occurred ones in blue moon and the frequencies are not so high as other emergencies, but these kind of incidence have high threat, large ramification and sometimes difficult to manage by single agency approach. This situation requires high persistence, adequate resources, right tools and equipment as well effective training & education among the responders for success of operations.
It seen in our country the big cities and metros as well industrial fire department have facilities with such equipment which useful especially in hazmat response. The unavailability and high cost as well limited budget of small fire department need mutual cooperative response with government and non-government agencies. Effective training for hazmat identification and reorganization of hazmat are mostly helpful but in some critical cases the symptoms and signs are not sufficient to understand the hazard related to hazmat. At this moment the instrument plays vital and important role to gather information and help to plan safe response and successful operations. Use of instrument and understanding the operation and working principle is part of technical level curriculum of the skill and need basic understanding of the principle of physics and chemistry. The main purpose of identification of hazardous chemical to cope with its hazardous property and help to choose appropriate level of PPE and also help to reduce to fall the situation in more critical and disastrous. Different type of instruments are use to determine the hazardous property of chemical, the most hazmat are in form of gaseous, liquid and solid particles. In all cases different types of detection instruments use by the responders, it is also important to sampling of hazmat atmosphere is a key skill in detection through instruments.
When we look back, the identification of hazardous chemicals or atmosphere is start with the miner’s cannery, a bird the coal miners keep with them. We can say it is biological sensor for hazardous atmosphere. This bird is sensible to Hydrogen sulfide and carbon monoxide, in a small amount of this gases ill effect on bird and the bird keeper warn the miners to retrieve in case for presence of hazardous gases.
Mostly detection instruments are uses by fire service to handle the hazmat operation are gas detection instruments, because the concentration of gases in atmosphere is more critical rather than solid and liquid phase of material. Some volatile liquid vapors also measured due to explosive, irritant and toxic properties with these instruments. Most fire service responders have reasonable knowledge upon the use of instruments, it is expected that the first responder in fire service should have at least firsthand knowledge and skill to handle the instruments. The technology is ever changing in the field of gas monitoring, new instruments and gadgets are emerging every year and old one absolute after some time. The instrument use by today may be not in production after two years. So it is important while selecting and purchasing of instruments, it should be usable and customer support by manufacturer for reasonable period of time. It is also important to evaluate the requirements, operation, basic feature, usefulness and price of instrument before purchase and procurement.
In most departments recommended multi gas detectors including explosive or LEL detector along with toxic gases and Oxygen level. Normally the multi gas detectors are combined CO (carbon monoxide) and H2S (hydrogen sulfide). Some department chooses instead Cl (chlorine) and SO2 (sulfur dioxide). Personal gas monitors are widely use in industrial environment as part of safety work culture. Even though these instruments are considered expensive for fire department, but in comparison of other equipment it seems inexpensive. In our country fire department procures this kind of instruments mostly without training, or some time the training is insufficient to handle the equipment, which is deleterious to the effective use of instruments. It should be kept in mind when purchasing these gas detection instruments with several maintenance equipment; it is also advisable to arrange training and maintenance contract with the supplying agency or manufacturer. So while the functioning of the instruments not effect on the operations. Generally this kind of equipment available with its accessories in form of kit included sampling pump, calibration gas, and hardware; in some cases software also. Calibration gas supplied with single gas or mixture of gases for multi gas detection instrument, the gas also had expiry date which needs to replace, generally in six month. The detectors need to be calibrating time to time as recommended by manufacturer. The instrument has power supply by rechargeable batteries or dry cell, in case of rechargeable batteries need the charge the instrument and in case of dry cell it need to replace when cell charge weaken.
Censors of detectors need to be change, in case which indicates failure. Manufacturer provided one or two years of warrantees on censors. Broadly the LEL sensors has warrantees of four to five years, CO and H2S sensors provided with 12 to 24 moths warrantees and O2 sensor 12 month or two or three month more warrantees, and other sensors with 6 month to 24 months of warrantees. It mostly depends on the manufacturer and the technology used in sensor. The life of sensor is fixed by the manufacturer and it may shorten by wear and tear as well non-recommended operation of instruments.
This kind of instruments is delegate in nature of operation and functioning, a small defect lead to malfunction of instrument in that case the reading of detector may not actual. But now a day the instrument provided with self diagnosing technology, where it works properly or will not work, so probability of failure during operation is avoided.
Most electronic gas/vapor detection instruments are based on scientific principles and different technology in vary to range and performance. Each and every technology has their limitation, with the exception of the new innovations and researches emerging to enhance performance, reliability and overcome to limitation. The common sensor technologies used in electronic based gas detections instruments are:
- Catalytic bead (cat bead) sensors.
- Infrared sensors.
- Electrochemical ( E-Chem) sensors.
- Photo ionization detector (PID).
- Metal oxide semiconductor (MOS) sensors.
Apart from that, there are some simple technologies also use to by HAZMAT response team. Colorimetric sampling is one of the reliable and simple technique use where know or unknown toxic as well combustible gases are presents. The colorimetric sampling consisting two major equipment one is the glass tube which sealed both side and filled regent (powder or crystals) companion with air drowning pump. Now a days the automatic detector tube pump also available. And also some pump with attachment facility to measure one or more gases simultaneously with single operation. The colorimetric detection tubes need to break from seal at both side before attaching the port of pump to collect sample, which is consumable supply and only use one time. Detection tubes are available calibrated marking or non marking variants. The main benefit of this instrument no need of specific training, simple instructions and little training is sufficient to operate the instrument.
A new system has been developed to measure spot measurement of hazardous gases. This system knows as Chip Measurement System. Which  also a reliable and portable system, can detect various gases as accurate the electronic detection system. This system based on optoelectronic analysis system. The defining two element of the system are the analyzer and the chip, which is substance specific. The provided chips are generally pre calibrated in factory so no need of calibration before operation. Commonly the analyzer unit consisting a pump within and powered by dry cell batteries. The system is easy to operate as the colorimetric system as well sophisticated as electronic detection system.
PH strips are commonly use to know the property of liquid for determine acidity and alkaline. As well the detection paper strips are use for detecting chemical warfare agents by some hazamat units.
Terminology related to hazardous gas/material detection and measurement.
Aerosol is a suspension in air(or gas) to minute particles of liquid or a solid.
Alarm set point is the selected gas concentration level where an alarm is activated.
Analyzer is an instrument which can determine qualitative and quantitatively the specific compound in the mixture.
Bump test Used to determine if an air monitor is working. It will alarm if a toxic gas is present. It is quick check to make sure the instrument is respond to a sample of gas.
Calibration is the procedure use to adjust the instrument for proper response.
Calibration gas is the known concentration of gas to set the instrument span or alarm level.
Reaction time is the lag time which is related to response of the detector to the suction of air through air pump. Which is very manufacturer to manufacture.
Recovery time is the amount of time it takes the monitor to clear the air sample.
Relative response is the way monitor or detector reaction to a gas other than the one which is calibrated for. When non profile gas is detected the monitor shows different value rather than actual one.
LEL Lower Explosive Limit
PPM Particle Per Million
Multi gas detector a term to describe an air monitor that measures oxygen levels, explosive levels and one or two toxic gases simultaneously.
Sensor a gas detecting sensor converts the presence of gas or vapor in to an eclectically measurable signals, the sensor is the heart of the gas monitor.
Zone is the term to hazardous area classification, where the presence of combustible gas or vapors in atmosphere, which is relative to use electronic instruments as per safety standard.
TLV Threshold Limit Value
STEL Short Term Exposure Limit
TWA Time Weighted Average
Exposure Limit is concentration of substances under which it is believed that nearly all workers can be exposed on daily basis without any adverse effects.
Explosimeter is the term use for combustible gas detector.
Gas monitor is the term use for same instrument use of hazardous gas detection.
