All Products

91030-XLT EdgeHD 8 Optical Tube Assembly by Celestron

• Experience our best optical performance with EdgeHD's aplanatic, flat field Schmidt-Cassegrain optics for pinpoint stars all the way to the edge of today's largest imaging sensors and widest eyepieces.
• Aluminum optical tube with tube vents featuring an integrated 95-micron mesh filter allows hot air to be released from behind the primary mirror. Mirror support knobs hold the mirror in place and reduce image shift during imaging.
• Versatile design accommodates 3 focal ratios: native f/10, f/7 with the addition of a focal reducer, or ultra-fast f/2 imaging with a removable secondary mirror and third-party accessories.
• Celestron's premium StarBright XLT coatings provide maximum light transmission.
• A 9x50 finderscope, 1.25" mirror diagonal for more comfortable viewing, and 40 mm Plössl 1.25" eyepiece are all included.
• CGX 800 HD combines Celestron's all-new state of the art CGX computerized equatorial mount with its acclaimed EdgeHD optical system. With 8 inches of aperture and our premium StarBright XLT coatings, the CGX 800 HD gives you over 800 times the light gathering power than the unaided eye and is the lightest and most portable telescope in its class.

See the Universe in HD

EdgeHD is an aplanatic, flat field Schmidt-Cassegrain telescope that produces aberration-free images across a wide visual and photographic field of view. The optical system was designed to reduce more than just off-axis star coma; it also provides an astrograph-quality flat focal plane all the way to the edge of the field of view.

True Astrograph Quality

Many optical designs that advertise themselves as "astrographs" actually only produce pinpoint stars across a curved focal plane. While this may be acceptable for some visual observing, stars will appear out of focus at the edge when used with the flat chip sensor of a digital camera. EdgeHD optics produce a focal plane more than three-times flatter than a standard Schmidt-Cassegrain telescope and dramatically flatter than competing coma-free designs. This guarantees you visibly sharp stars across some of the largest CCD chips available today. Learn more about EdgeHD technology.

Improved Performance

Superior edge performance not only creates rounder, more pleasing stars, but actually improves the resolution and limiting magnitude when compared to telescopes of equal aperture. With Celestron's StarBright XLT optical coatings on every surface, EdgeHD optics gives you maximum light throughput across the widest visual and photographic spectrum.

Mechanical Features

In addition to EdgeHD's optimized optical design, the telescope tube has been redesigned to make sure you get the most from your optics each and every night.

• Mirror clutches - Flexible tension clutches hold the mirror in place and reduce image shift when taking long exposure astro-images. Once focused, the flexible rods allow the mirror to be held in place without putting any force or pressure on the mirror assembly, keeping the image centered in the eyepiece (or on the sensor).
• Tube vents - Cooling vents located on the rear cell allow hot air to be released from behind the primary mirror. Each vent has an integrated 95-micron micromesh filter guaranteed to let warm air out without letting dust in.
• Fastar versatility - EdgeHD is the most versatile imaging telescope available today. At its native f/10, you can achieve the image scale necessary to capture the smallest of deep sky objects. Add the optional reducer lens custom-designed for your size EdgeHD tube and you can increase your field of view without sacrificing optical performance. A Barlow gives you added power for high-resolution planetary, lunar and solar imaging. All EdgeHD optical tubes are Fastar-compatible, allowing the secondary mirror to be removed and replaced with a third party lens accessory for ultra-fast f/2 wide field imaging.

Individually Tested

Every EdgeHD that ships has been tested not only for the surface quality of each optical component, but also with a camera and artificial star to ensure the imaging system meets our rigid quality assurance. This "final acceptance test" confirms the EdgeHD will perform in the field and deliver high-quality astroimages.

*Please note we can only ship RKI products to customers within the United States

SRPN28B Cool Guardian R717 (NH3): Refrigerant gas detector with electrochemical sensor for R717 (NH3); measuring scale: 0...100 ppm by Seitron Americas

Cool Guardian Refrigerant Leak Detector, uses fast response time, low-temperature performance (-40..+122°C / -40..+50°F), and integrated audio and visual alarms, simplifies and facilitates compliance and safety regulations.

Modern refrigeration systems are engineered for optimal efficiency and airtight integrity. However, improper installation, unintentional damage, or mechanical wear and tear can potentially lead to dangerous gas leaks.

In this context, Cool Guardian gas transmitter serves as a vigilant guardian against unforeseen leaks, which could compromise both the environment and human health.

Applications

Selection of the appropriate gas sensor to monitor the presence of refrigerants in industrial processes, commercial cooling systems, or refrigeration facilities is crucial when it comes to fixed gas transmitters. These transmitters are designed to accurately detect and measure various refrigerant gases, providing essential data for maintaining the integrity of refrigeration systems and preventing potential leaks.

Industrial Refrigeration

Large-scale refrigeration systems in industries like food processing, pharmaceuticals, and cold storage facilities rely on refrigerant gas. Leak transmitters help detect leaks promptly, preventing environmental damage and ensuring the safety of workers.

Mechanical Rooms

Mechanical rooms can pose safety risks due to the presence of different gases. Refrigerant gas leak transmitters continuously monitor the environment for leaks, ensuring the safety of personnel working in these areas by promptly detecting any gas leaks.

Process Cooling / Chillers

Chiller systems often use refrigerants to maintain specific temperatures for industrial processes. Leak transmitters provide continuous monitoring, ensuring that any leaks are promptly detected to prevent disruptions in the cooling process.

HVAC Systems

Heating, ventilation, and air conditioning (HVAC) systems in commercial buildings, hospitals, hotels, and shopping malls use refrigerants. Leak transmitters aid in monitoring and detecting leaks.

Laboratories and Research Facilities

Laboratories, especially those handling sensitive materials or operating with precise temperature control, utilize refrigeration systems. Leak transmitters play a critical role in maintaining the integrity of experiments and preserving samples by promptly detecting leaks.

*Please note we can only ship RKI products to customers within the United States

G460-11-01-02-60-44 G460 Multi-Gas Detector with Alkaline Smart Pump and NiMH Battery with Flashlights, O2, Catalytic Combustion LEL Sensor, CO, H2S, CO2, NDIR by GfG

For over 50 years, GfG Instrumentation has worked to develop the most reliable and effective equipment for gas detection and measurement technology. Developed by a team of highly experienced scientists and specially trained engineers, GfG products are high quality reliable instruments designed to meet the unique needs of potentially hazardous worksite. With the introduction of the G460 Multi-Gas Detector, GfG Instrumentation is continuing the trend.

G460 Multi-Gas Detector

The G460 Multi-Gas Detector is a compact and robust system with the capabilities of detecting up to six different gases and simultaneously displaying the readings. The portable detector features a user friendly and intuitive interface to simplify the day to day operations.

Ease of Use

For typical daily operations, the G460 Multi-Gas Detector operates with a single button. The complete user interface can provide access to advanced setup options with three buttons. The unit also features easy calibration operation. Simply attach the calibration adapter and apply gas. The G460 will automatically perform the appropriate adjustments. The detector will then store the dates of the three most recent calibrations for each sensor.

The G460 also features a large easy to read tricolor display which uses a color code to indicate the alarm severity. From green to orange to red, the tricolor display is intuitive and incredibly user friendly. The display feature can also flip or zoom with the touch of a button. The G460 multi-faceted alarm system also includes an ultra loud audible buzzer at 103 dB, a standard vibration mechanism, and 360 bright LED alerts (the LED alerts can also be equipped to function as flashlights). This multi-faceted system is sure to alert users and those nearby of the potential hazardous conditions. For smooth and continuous operations, the G460 Multi-Gas Detector uses interchangeable alkaline and rechargeable battery packs that provide up to 25 hours of continuous operation. Using a drop in cradle charger, the rechargeable pack can completely recharge in less than 4 hours.

G460 Multi-Gas Detector Features

The G460 Multi-Gas Detector features a motorized pump with a built-in diffusion or sample draw mode switch. The hose is easily attachable and can draw from 100 feet away. The hose is powered by its own battery pack that provides 20 hours of continuous operation. The multi-gas detector also features the widest range of sensors on the market. The compatible long lasting (and interchangeable) smart sensors include LEL, SO2, O2, H2, H2S, NO, CO, O3, HF, NH3, CIO2, CI2, PH3, ETO, HCN, and NO2. Users can purchase additional sensors to help customize the unit such as infrared sensors for the measurement of CO2 and photoionization sensors for volatile organic chemical hazards. The G460 has standard data logging capabilities that store up to 55 hours of the most recent activities. Alarm activations gas thresholds and stored permanently in the internal memory. Employers can download all internal information to generate reports and monitor results.

*Please note we can only ship RKI products to customers within the United States

12031 Advanced VX 8" EdgeHD Telescope by Celestron

Advanced VX 8" EdgeHD: truly the ultimate entry-level astroimaging package. This package combines the groundbreaking new Advanced VX mount with Celestron's best optics, the EdgeHD optical system. This setup offers the astroimager maximum versatility - allowing up to 3 different f-stop configurations. Users can attach a camera to the rear of the telescope and shoot at f/10, or attach our 8-inch focal reducer and shoot at f/7. Additionally, EdgeHD is Fastar/Hyperstar compatible, giving imagers the option to shoot at ultra-fast f/2. No matter which configuration you choose, EdgeHD technology gives you pinpoint stars all the way to the edge of the CCD sensor.

With an 8-inch optical tube and our portable Advanced VX mount, this setup can be easily transported and assembled by one person. You'll also have plenty of load capacity to attach your camera and other accessories. This setup is simple enough for a beginner to use, but can also provide years of enjoyment for sophisticated astroimagers.

• 8" (2032 mm) f/10 Edge HD includes StarBright XLT coatings for better light transmission
• Edge HD optical design fully corrects for coma and field curvature, delivering a truly flat field
• Built-in tube vents with integrated 60 micron mesh filters allow hot air to be released behind the primar mirror
• Fastar compatible tube comes with removable secondary mirror for fast f/2.8 imaging
• 9x50 optical finderscope for locating alignment stars
• Integer gear ratios and permanently programmable Periodic Error Correction eliminates recurring track errors from the worm gear.
• Autoguider port for long exposure imaging
• New motors offer improved tracking performance & provide more power to overcome load imbalances
• Updated industrial design offers more rigidity, less flexure and improved aesthetics
• New design allows viewing or imaging across the meridian without interference from the motors housings
• Improved latitude range. Can be used between 7 - 77 degrees latitude.
• NexStar hand control offers multiple language programming (English, French, Italian, German, Spanish)

About the Mount

The new Advanced VX mount was specifically designed to provide optimum imaging performance for smaller telescopes. Now your smaller telescope can take advantage of All-Star Polar Alignment and autoguider support. You'll be able to track through long exposures using permanently programmable periodic error correction. Image across the meridian without doing a meridian flip, so you can seamlessly image the best part of night sky. Advanced VX features significantly larger base castings than our previous design, improving stability under heavier loads. Improved motors offer more torque and can handle slight load imbalances with ease.

Part Number: SRWMCDUM

65-2611RK M2, Hydrogen (H2) Specific 0 - 100% LEL Sensor/Transmitter with J-Box, UL Version by RKI Instruments

RKI Instruments uses the latest cutting edge technology when developing transmitters and sensors. Its dedication to workplace safety and reliable safety solutions is unparalleled. The M2 Stand Alone Transmitter utilizes state of the art sensor cell technology to integrate workplace safety with the industry's more advanced transmitter technologies.

M2 Stand Alone Transmitter

The M2 Stand Alone Transmitter is operational with or without a controller and is available in two forms: explosion proof and non-explosion proof. The unit has a backlit screen for a direct digital readout, and a user friendly setup with push buttons and easy to read LCD menus. The advanced technology transmitter can function as an independent standalone system or as part of an integrated detection and transmission system. Using state of the art technology, the transmitter uses a magnetic want technique for performing non-intrusive calibration. For optimal stability and accurate readings, the unit provides an automatic zero drift correction feature. This also reduces the need for adjustments due to sensor aging.

The M2 Stand Alone Transmitter is available for LEL, H2S, CO, PPM, HC, CO2, CI2, NH3, SO2, HCN, and more. The unit also features an infrared sensor for CO2 and combustible gases. With 2 fully programmable alarms and a fail relay, the visual color coded LED alarms are reliable and customizable to meet specific needs.

Advanced sensor technology

The state of the art sensors are long lasting with a lifespan typically over two years. Sensor construction is rated Class I, Division 1 groups B, C, and D for flammables, CO, H2S, O2, and CO2. The sensors are rated Class I, Division 2 for all other toxic gases. Depending on the gas, the sensors will operate through a catalytic, galvanic cell, electrochemical, or infrared design. The plug in nature of the sensors allows for a quick and tool free onsite replacement.

Specifications

Each transmitter features 2 to 3 years of life with normal service. The explosion proof LEL H2 specific transmitter has 3 to 5 years with normal service, and the explosion proof carbon dioxide, methane, and hydrocarbons feature over 5 years of life with normal service. The explosion proof transmitters are also water repellant. Each device is approximately 8.5 H x 5.2 W x 4.5 D and features an alphanumeric display with a backlight. The screen displays 8 characters per line with 2 lines for gas concentration readouts.

Optional Accessories

The M2 Stand Alone Transmitter has a variety of optional accessories available including calibration adaptors, flow through adaptors, remote horns and lights, calibration kits, battery backups, splash guards, air aspirator adaptors or panels, and dataloggers. The transmitters are directly compatible with Beacon 110, 200, 410, and 800 controllers.

*Please note we can only ship RKI products to customers within the United States

Part Number: M107218VN

72-5520RK-XX Eagle Portable Monitor for LEL & PPM/O2/CO/CO2/NH3 (Specify CO2 Range) by RKI Instruments

The Eagle Portable Monitor can simultaneously detect up to 6 different gases. With over 400 gas monitoring configurations, the unit can detect a wide range of toxic gases. RKI Industries offers long life protection for workplace safety and hazardous jobsites. With a reputation for advanced engineering and state of the art technology, the RKI Industries' Eagle One to Six Gas Portable Monitor is an industry leader in accuracy and affordability.

Features

The Eagle One to Six Gas Portable Monitor is available with a wide variety of exclusive features. The unit is capable of PPM/LEL hydrocarbon detection and for environmental use, has a methane elimination switch. The dual hydrophobic filters (available on some models) ensure quality control. To preserve the integrity and safety of the device, the portable monitor also has an adjustment lockout switch to prevent tampering. For quick and easy testing, the monitor offers autocalibration and single gas calibration.

The Eagle is housed in an ergonomic RFI, EMI, chemical, and weather resistant polycarbonate and polyester enclosure. It can operate in the rain or in 2 inches of water without damage. It features an ergonomically designed top handle to ensure durability.

Accessories and Options

IR Sensors are available for CO2, % LEL CH4 or HC, and % volume CH4 or HC. Each unit also has datalogging capabilities for research, evaluation, and analysis of worksite atmospheres. The unit comes standard with several accessories including a shoulder strap, alkaline batteries, a hydrophobic probe, a 5 foot hose, and an internal hydrophobic filter with most models. Optional accessories can be purchased to fully customize the portable monitor to meet specific needs including a datalogging kit, remote alarms, dilution fitting, Ni-Cad batteries, battery chargers, continuous operation adapter, extra loud buzzer, extension probes, and large internal hydrophobic filter.

Specifications

The Eagle has a battery life of up to 30 hours of continuous operation with alkaline or Ni-cad capability and a sensor life of approximately 2 years. Its standard weight is approximately 5 pounds with dimensions of 10.5 L x 5.9 W x 7 H. The formidable long life pump (with a life of approximately 6,000 hours) reaches up to 125 feet in range with filters and has a low flow pump shut off and alarm. The unit has a response time of up to 30 seconds for most gases, and features a double alarm of audible alerts at 85 dB and visual alerts of dual high intensity LEDs and a flashing display screen.

The display screen is an easy to read 4 x 20 LCD readout. The backlit display sits at the top of the unit for full visibility, and displays the readings and statuses of 4 channels simultaneously.

The portable monitor is rated as intrinsically safe and has a standard 2 year warranty for materials and craftsmanship.

*Please note we can only ship RKI products to customers within the United States

Sperian Biosystems PhD6 Multigas Detector

The Biosystems PhD6 Multigas Detector is the latest development in compact multigas detection systems. The detector is proven to be compact, efficient, and cost effective. With dual alarm systems featuring ultra-loud audible indicators and ultra-bright LED visual indicators, users and those nearby are always notified when potential hazards may be present. When developing this detector, the engineers at SperianProtection Instrumentation also developed an express docking station that would reduce calibration time and labor costs. The detection and docking station help users meet record keeping requirements and reduce the risks of human error. With the SperianBiosystems PhD6 Multigas Detector, users can rest assured that they are receiving the very best in gas detection technology.

Key Features

The Biosystems PhD6 Multigas Detector is compatible with over 19 sensor choices including:

• PID
• IR-CO2
• IR-CH4
• Conventional LEL
• Oxygen
• 15 different toxic gas sensors

The gas detector is encased in a durable solid polycarbonate case with a rubber over mold for easy handling. It has an interchangeable battery pack with both Alkaline and Li-Ion rechargeable batteries. Both battery types offer up to 24 hour run times. The unit features dual audible alarms at 92 decibels and front and side ultra-bright LED visual alarms to ensure that the user and those nearby are always notified of possible hazardous conditions. For easy interpretation, the detector has an easy to read status bar and large LCD display that notifies users of the device s functionality and calibration due date. Using the menu options, users can easily adjust a variety of the instrument s settings.

Automatic Docking Station

When developing the PhD6 Multigas Detector, product developers also created an automatic docking station (Biosystems IQ6 Express Dock) to be fully compatible with the detector. The docking station aims to reduce labor time and costs by fully automating certain aspects of instrument maintenance including calibration, functionality testing, and record keeping. Using the Express Dock, users can maintain compliance with recordkeeping requirements by simply docking the detector in the station. The station will automatically perform a variety of operations without user intervention.

Sperian Protection Instrumentation and Honeywell

Sperian Protection Instrumentation is a global leader in personal safety equipment. The company was recently acquired by Honeywell, another global leader in technology and innovation. As a Fortune 100 company, Honeywell has a vested interest in maintaining its reputation as a developer of efficient and reliable safety equipment. Sperian Protection Instrumentation helps to expand Honeywell s personal safety offerings while advancing their position in the American market. By purchasing a product by Sperian and Honeywell, customers can be assured they are receiving the very best in safety technology and equipment.

Part Number: M197150LM26

MAB3-A2C112E-020 MultiRAE Lite Pumped Portable Multi-gas Monitor - 10.6 eV PID / LEL / H2S / CO / O2 / Li-ion / Non-Wireless by RAE Systems

The MultiRAE Lite is the optimal one-to-six1-gas monitor for personal protection and leak detection applications. The MultiRAE Lite is available in pumped and diffusion versions and features the broadest selection of sensor options in its class. The MultiRAE Lite can be configured to exactly meet the detection needs and compliance requirements of various countries, industries, and applications.

The MultiRAE Lite's optional wireless capability improves safety by providing commanders and safety officers real-time access to instrument readings and alarm status from any location for better situational awareness and faster incident response.

Key Features

• Wireless access to real-time instrument readings and alarm status from any location
• Unmistakable five-way local and remote wireless notification of alarm conditions including Man Down Alarm
• Over 25 interchangeable sensor options, including PID for VOCs, NDIR and catalytic for combustibles, and NDIR for CO₂
• Intelligent sensors store calibration data, so they can be swapped in the field
• Large graphical display with easy-to-use, icon-driven user interface
• Continuous datalogging (6 months for 5 sensors, 24x7)

Applications

• Chemical
• Food and beverage
• Oil and gas (downstream)
• Pharmaceutical
• Telecommunications
• Wastewater treatment
• Fire overhaul

G460-11-03-24-00-10 G460 Multi-Gas Detector With NiMH Battery, O2, Catalytic Combustion LEL Sensor, CO and H2S Sensor, NO2 by GfG

For over 50 years, GfG Instrumentation has worked to develop the most reliable and effective equipment for gas detection and measurement technology. Developed by a team of highly experienced scientists and specially trained engineers, GfG products are high quality reliable instruments designed to meet the unique needs of potentially hazardous worksite. With the introduction of the G460 Multi-Gas Detector, GfG Instrumentation is continuing the trend.

G460 Multi-Gas Detector

The G460 Multi-Gas Detector is a compact and robust system with the capabilities of detecting up to six different gases and simultaneously displaying the readings. The portable detector features a user friendly and intuitive interface to simplify the day to day operations.

Ease of Use

For typical daily operations, the G460 Multi-Gas Detector operates with a single button. The complete user interface can provide access to advanced setup options with three buttons. The unit also features easy calibration operation. Simply attach the calibration adapter and apply gas. The G460 will automatically perform the appropriate adjustments. The detector will then store the dates of the three most recent calibrations for each sensor.

The G460 also features a large easy to read tricolor display which uses a color code to indicate the alarm severity. From green to orange to red, the tricolor display is intuitive and incredibly user friendly. The display feature can also flip or zoom with the touch of a button. The G460 multi-faceted alarm system also includes an ultra loud audible buzzer at 103 dB, a standard vibration mechanism, and 360 bright LED alerts (the LED alerts can also be equipped to function as flashlights). This multi-faceted system is sure to alert users and those nearby of the potential hazardous conditions. For smooth and continuous operations, the G460 Multi-Gas Detector uses interchangeable alkaline and rechargeable battery packs that provide up to 25 hours of continuous operation. Using a drop in cradle charger, the rechargeable pack can completely recharge in less than 4 hours.

G460 Multi-Gas Detector Features

The G460 Multi-Gas Detector features a motorized pump with a built-in diffusion or sample draw mode switch. The hose is easily attachable and can draw from 100 feet away. The hose is powered by its own battery pack that provides 20 hours of continuous operation. The multi-gas detector also features the widest range of sensors on the market. The compatible long lasting (and interchangeable) smart sensors include LEL, SO2, O2, H2, H2S, NO, CO, O3, HF, NH3, CIO2, CI2, PH3, ETO, HCN, and NO2. Users can purchase additional sensors to help customize the unit such as infrared sensors for the measurement of CO2 and photoionization sensors for volatile organic chemical hazards. The G460 has standard data logging capabilities that store up to 55 hours of the most recent activities. Alarm activations gas thresholds and stored permanently in the internal memory. Employers can download all internal information to generate reports and monitor results.

98766-09 Traceable 300-Memory All Function Digital Stopwatch with Calibration by Digi-Sense

Three-line display on this multipurpose stopwatch/timer/chronograph shows running time, cumulative-split, and interval-split - simultaneously. Easily repeat functions of countdown alarm timing as a stopwatch. Set timer to count down at any time from 10 hours to 1 second. When zero is reached, the timer alarms and begins to count down again from the programmed time. The repeat cycle continues automatically, or until stopped.

Display always shows running time remaining to zero and cycles counted from 1 to 300. Stopwatch also includes pacer, stroke, and speed calculation functions. As a chronograph, the unit displays time of day in hours, minutes, and seconds, AM/PM, date, and day of the week. O-ring sealed water- and shock-resistant ABS plastic case has nonskid rubber edges.

Traceable® Products have an individually-numbered Traceable® Certificate provided with each unit, that assures accuracy from our ISO/IEC 17025:2017(1750.01) calibration laboratory accredited by A2LA. It indicates traceability of measurements to the SI units through NIST or other recognized national measurement institutes (NMI) that are signatories to the CIPM Mutual Recognition Agreement. Each product goes through an intense vetting process before it can carry the Traceable name, thus saving you both time and money by not having to calibrate separately.

• Includes NIST-Traceable certificate from our A2LA accredited (1750.01) calibration laboratory
• Recall up to 300 memories both during and after event timing
• Set time-of-day alarm
• Pacer function works great for physical education tests

Includes

One 3 V button cell, lanyard, and NIST-traceable calibration certificate with data.

BZ1-0110000111 Radius BZ1 Area Monitor, CO DualSense, Without Pump, UL/CSA, LENS™ Wireless, English by Industrial Scientific

When it comes to choosing equipment to protect your worksite from gas hazards, rely on the Radius® BZ1 Area Monitor. No other area monitor protects your workers longer in the field with less setup, user training, and time in the shop.

• Detect up to seven gases using 22 sensor options including PID
• Longest running area monitor with a typical run time of 7 days (168 hours)
• Extended Run Time Power Supply can extend battery to over 1 month
• Ultra-bright blue and red lights and attention-grabbing alarms with distinctive tones
• Audible alarms sound at 108 dB at 1 m to cut through high-noise environments
• Largest display of any area monitor on the market
• Intuitive text-based navigation and configuration
• Customizable alarm action messages such as "EVACUATE" or "VENTILATE"
• LENS™ Wireless enables communication between area monitors and Ventis® Pro5 personal monitors
• All-weather sensor deployment and 360-degree gas path for more accurate detection
• DualSense® Technology increases worker safety by using two sensors to detect the same gas