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Forensics Detectors 4 Gas Meter for Confined Space (O2, CO, H2S, LEL)
$199.00
Final price set by Amazon · may vary
Editor’s note: the Forensics Detectors 4 gas meter is one of the portable instruments we curate in our Portable Gas Detectors buyer’s hub. Compare it head-to-head with the Forensics Detectors USB 4 Gas Monitor belo...
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Editor’s note: the Forensics Detectors 4 gas meter is one of the portable instruments we curate in our Portable Gas Detectors buyer’s hub. Compare it head-to-head with the Forensics Detectors USB 4 Gas Monitor below before you order.
Expert reviews & buying guides: Read our full Forensics 4 Gas Meter review. See our best 4-gas monitor guide. Compare it: Forensics 4 Gas Meter vs Pump, 4-Gas vs Single-Gas.
Forensics Detectors 4 Gas Meter — Confined-Space O2, CO, H2S & LEL Monitor
The Forensics Detectors 4 gas meter is a NIST-calibrated, confined-space-ready monitor that reads oxygen (O2), combustible gas (LEL), carbon monoxide (CO) and hydrogen sulfide (H2S) in one pass — the four-hazard set portable gas detector buyers need for permit entry. At 4.8 oz with triple alarms, it is built for field crews who want documented accuracy without a fleet-management contract.
Jump to: Features · Specs · What it detects · Comparison · FAQ
The Forensics Detectors 4 Gas Meter is a battery-powered, electrochemical four-gas monitor (O2, CO, H2S, LEL) with a NIST calibration certificate, designed for portable confined-space pre-entry testing.
Key features
- Reads all four confined-space hazards — oxygen (O2), combustible gas (LEL), carbon monoxide (CO) and hydrogen sulfide (H2S) — on one screen
- Ships with a USA NIST calibration certificate so you can document instrument accuracy from day one
- Triple alarm — adjustable audible, visual LED and vibration — for noisy or low-visibility work
- Electrochemical nano sensors with zero and span calibration options for ongoing accuracy
- Rugged anti-slip ABS housing that is water-resistant, dust-proof and explosion-resistant
- Light 4.8 oz body that clips to a belt or harness for pre-entry checks
Pros
- NIST calibration certificate included
- Highest customer rating in our portable lineup (4.9/5)
- Adjustable audible, visual and vibration alarms
- Very light at 4.8 oz
- Zero/span field calibration supported
Cons
- Diffusion sampling only — no built-in pump for remote pre-entry testing
- Field/value-grade; not a managed-fleet instrument like Industrial Scientific or BW Honeywell
- Electrochemical sensors need periodic replacement (typically every 2–3 years)
- Single unit — no docking-station bump/cal automation
Specifications
| Specification | Detail |
|---|---|
| Gases detected | O2, CO, H2S, LEL combustibles |
| Sensor type | Electrochemical (nano sensors) |
| Alarms | Audible, visual (LED) & vibration, adjustable |
| Calibration | Zero & span; NIST certificate included |
| Power | Rechargeable battery |
| Weight | 4.8 oz |
| Dimensions | 2.6" x 1.2" x 5.1" |
| Build | High-strength ABS, water/dust/explosion-resistant |
| Color | Yellow |
Where the Forensics Detectors 4 Gas Meter fits
- Confined-space pre-entry atmosphere checks
- Sewer, vault and manhole spot tests
- Tank and vessel entry monitoring
- HVAC, boiler and mechanical-room checks
- General industrial walk-around monitoring
What the Forensics Detectors 4 Gas Meter detects (and what it doesn’t)
This meter measures oxygen (O2), combustible gas (LEL), carbon monoxide (CO) and hydrogen sulfide (H2S) — the standard four-gas set for confined-space entry. It does not read volatile organic compounds (VOCs), CO2, or single toxics such as chlorine or ammonia; those need a dedicated PID or gas-specific sensor. It uses diffusion sampling, so it reads the air around it — to draw a remote sample from the bottom of a tank before entry, choose the Forensics Detectors 4 Gas Monitor with Pump instead. Keep it accurate with zero/span calibration and a periodic bump test using standard four-gas calibration gas. For all-shift single-worker wear, pair it with a clip from Personal & Wearable Gas Detectors.
Cross-shopping? This unit sits in our Portable Gas Detectors hub alongside the Forensics Detectors USB 4 Gas Monitor, TopTes Guard-863Pro, TopTes Guard-101, TopTes Guard-156. If one worker needs all-shift wear instead of a carried meter, see Personal & Wearable Gas Detectors; for a fixed install or a job-site perimeter, see Fixed Gas Detection Systems and Area & Transportable Gas Monitors.
Forensics Detectors 4-gas family compared
| Model | Sampling | NIST cert | Recharge | Street price |
|---|---|---|---|---|
| 4 Gas Meter (Confined Space) | Diffusion | Yes | Battery | ~$199 |
| 4 Gas Monitor (USB) | Diffusion | Yes | USB rechargeable | ~$225 |
| 4 Gas Monitor + Pump | Motorized pump + probe | Yes | USB rechargeable | ~$299 |
- Choose this 4 Gas Meter for the lightest, lowest-cost NIST-certified diffusion unit for routine pre-entry checks.
- Step up to the USB-rechargeable 4 Gas Monitor if you want USB charging and a higher review count.
- Move to the 4 Gas Monitor with Pump if you must sample remotely before entry.
Frequently asked questions
What gases does the Forensics Detectors 4 gas meter detect?
It detects oxygen (O2), combustible gas (LEL), carbon monoxide (CO) and hydrogen sulfide (H2S) — the four atmospheric hazards required for confined-space entry. For VOCs you need a separate PID unit; browse the full Portable Gas Detectors range for options.
Is the Forensics Detectors 4 gas meter NIST calibrated?
Yes — it ships with a USA NIST calibration certificate documenting instrument accuracy at the time of calibration. You should still bump-test before each use.
How do I calibrate and bump-test this meter?
Use standard four-gas calibration gas with the zero and span calibration functions. Bump-test before each day of use to confirm the sensors and alarms respond; do a full calibration on the manufacturer's schedule.
Can I use this for confined-space entry?
Yes — its O2/CO/H2S/LEL set matches the hazards OSHA 1910.146 names for permit entry. For pre-entry sampling of a sealed space, the pump version lets you test before anyone enters.
Does it have a pump or is it diffusion?
This model is diffusion — it reads the air around it. If you need to draw a remote sample through a probe, choose the Forensics Detectors 4 Gas Monitor with Pump.
How is it powered and how long does it run?
It runs on a rechargeable internal battery sized for a full work shift. Recharge between shifts so it is always ready for pre-entry checks.
What alarms does it have?
Adjustable audible, visual LED and vibration alarms trip when a gas reaches its preset level — useful in loud or low-visibility environments.
How long do the sensors last?
The electrochemical sensors typically last two to three years depending on exposure. Budget for sensor replacement and calibration gas as ongoing costs.
What does this meter NOT detect?
It does not read VOCs, CO2, or specific toxics like chlorine or ammonia. For those, a PID or gas-specific instrument is required — see the wider Portable Gas Detectors hub.
Is it in stock and how does it ship?
Stocked items ship through our Amazon fulfillment partner; use the buy button for current availability and delivery timing.
How does it compare to the USB-rechargeable Forensics monitor?
Both read the same four gases with NIST certificates; the USB 4 Gas Monitor adds USB charging and has more reviews, while this meter is lighter and lower cost.
Is this an industrial-grade instrument?
It is a NIST-certified field meter well suited to small crews and facilities. Large managed-fleet programs that need docking-station automation usually specify Industrial Scientific or BW Honeywell instruments.
Ready to order the Forensics Detectors 4 gas meter? Add it to your cart above, or check the current Amazon price below. Compare it against the rest of our Portable Gas Detectors lineup before you buy.
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Why trust this Forensics Detectors page? WC Safety is an independent industrial safety-equipment retailer serving safety managers, procurement teams and field supervisors. The specifications on this page are taken from the manufacturer’s published listing for Forensics Detectors 4 Gas Meter and framed against OSHA 29 CFR 1910.146 for confined-space atmospheric testing. Disclosed: WC Safety earns Amazon affiliate commissions on outbound clicks; that does not influence the specs shown or where this unit sits in our lineup.
By Steven Eaton, WC Safety Editorial — Industrial safety-equipment desk · specialization: portable atmospheric monitoring, confined-space gas detection and instrument selection.
Last updated: · Sources reviewed: manufacturer product listing & specifications, OSHA 29 CFR 1910.146, OSHA Annotated PEL tables, ACGIH Threshold Limit Values.
Editorial standard: Zero sponsored listings. No manufacturer input. Specs verified against the manufacturer’s published data.
Last updated: · Sources reviewed: manufacturer product listing & specifications, OSHA 29 CFR 1910.146, OSHA Annotated PEL tables, ACGIH Threshold Limit Values.
Editorial standard: Zero sponsored listings. No manufacturer input. Specs verified against the manufacturer’s published data.
How this page is maintained. Specifications and pricing are reviewed against the manufacturer’s current listing and re-checked whenever the lineup changes. Gas-detection guidance follows OSHA 1910.146 (permit-required confined spaces) and OSHA Permissible Exposure Limits, cross-referenced with ACGIH TLVs.
Disclosure. WC Safety participates in the Amazon Associates Program and earns commissions on qualifying purchases through outbound links on this page (tag wcsafety04-20). We are not sponsored by any instrument manufacturer. This page is buyer guidance, not medical, legal or regulatory advice — confirm gas-detection requirements for your site against the applicable OSHA standard and, for commercial monitoring programs, a Certified Industrial Hygienist (CIH).
Brand / Vendor
Forensics Detectors
Model / SKU
FD-4X
Product Type
Portable Gas Detector
Price
$199.00 (Amazon)
Rating
5.0 / 5 — 8 reviews
Availability
Check current availability on Amazon
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Every product earns its place based on safety credentials and field performance, not advertising spend.
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Every product listed on WC Safety is reviewed for standards compliance and safety credentials before publication.
Sourced for Professionals
Gear selected for safety managers, procurement teams, and field supervisors — not casual consumers.
Verified Buyer Reviews
Customer Reviews
★★★★★4.9 / 5· 23 ratings on Amazon
★★★★★
Solid 4-gas detector with strong features
Product title at the time of review:4 Gas Meter for Confined Space | USA NIST Calibration | O2, CO, H2S, LELThis meter is a straightforward, capable piece of safety gear that delivers excellent performance for the price, around $199.It's clearly designed for professionals working in hazardous environments, providing reliable real-time monitoring and alerts for toxic gases (CO, H2S), oxygen deficiency, and combustible gas risks via LEL detection.What I liked:* Compact and highly portable: roughly 5.1" tall and just 0.3 lbs (about 230g). It slips easily into a pocket or clips securely to a belt without adding bulk, ideal for fieldwork where mobility is key.* High-quality nano sensors: electrochemical for CO, H2S, and O2; catalytic for LEL.* Fast response: under 30 seconds, with practical resolutions: 0.1% for O2, 1 ppm for CO and H2S, 1% for LEL.* Effective alarms: loud buzzer, bright LEDs, and vibration ensure alerts aren't missed in noisy settings. Thresholds are fully adjustable.* Rugged build: rubberized high-strength ABS housing with anti-slip grip, solid water/dust resistance.* Simple operation: no complex menus or apps. Power on, zero if necessary, and you're ready to go.* Outstanding value: at this price, it stands out against many competitors in the compact yellow multi-gas category.A couple of notes:* Battery life: advertised as >24 hours on a full USB charge (2000 mAh Li-ion). On the first full charge, I only got about 15 hours of continuous use before low-battery shutdown. This could improve as the battery breaks in (common with new Li-ion cells), or it might vary based on alarm usage, backlight, etc. Still respectable for a shift or two, but don't count on the full advertised runtime right away.* Calibration certificate observations: the certificate is printed on A4 paper (not US letter size) with pre-printed results rather than handwritten ones. While the document claims calibration in their Los Angeles lab, these details suggest it may have been prepared or printed overseas (common for companies with global operations). This isn't necessarily a red flag, many reputable brands handle aspects of production/certification internationally, but it's worth noting. The NIST traceability itself appears legitimate.Overall, I highly recommend this detector if you're seeking a trustworthy, portable 4-gas monitor without premium-brand pricing. It includes a 1-year warranty, useful accessories (calibration cover, belt clip, manual, USB cable), and performs reliably for confined spaces, utility work, industrial sites, or any serious gas-safety needs.Great tool from a smaller USA-based brand that prioritizes quality and affordability. Strong performer with minor caveats on battery expectations and cert presentation.
Verified Purchaser · March 18, · ✓ Amazon Verified Purchase
★★★★★
This is accurate and trustworthy
This small USB rechargeable gadget monitors O2, CO, H2S, and LEL levels. It uses electrochemical sensors for CO, H2S, and O2, while the catalytic sensor is designed for EX LEL. You can expect it to last around two to three years, and it's best to recalibrate it every 12 months. As per the guidelines, it can measure oxygen levels from 0 to 30% with a precision of 0.1%, carbon monoxide from 0 to 999 parts per million, hydrogen sulfide from 0 to 100 parts per million, and combustible gases or LEL from 0 to 100% with a 1% resolution. Once it hits a preset level, the chosen audio, visual, or vibrating alarm will go off. It easily clips onto your clothes and has a firm grip. The rechargeable DC 3.7V Li-on battery, with a capacity of 2000 mAh, comes with a USB cable for charging. I got this for home use because my grandson and son work with a forge in my garage, and during winter, they often forget to open the windows or garage door. When you turn it on, it shows an oxygen level of 20.9% (dry air at sea level typically has about 20.95% oxygen by volume, with the remainder mostly nitrogen (78.08%) and small amounts of argon and carbon dioxide). The instructions explain how to recalibrate the device. If you buy this without any prior knowledge, going through the instructions and checking online resources will definitely help you get a better grasp of it.
Verified Purchaser · May 8, 202 · ✓ Amazon Verified Purchase
★★★★★
Way better than the disposable ones
Speed: Refresh rate is about once per second which is pretty typical of these meters.Accuracy: Reads identically to my other O2 and CO meters and it also has a zero cal and gas cal in the menus.Reliability: I haven't used this one enough to say for sure, but if it's made anything like my other Forensics meters, it should be 100% reliable.Battery life: Went from 80% to 40% in 6 hours so I estimate total battery life at around 15-16 hours. Note that this unit can be used while charging to extend runtime.Clip: aggressive and really grabs onto textiles without legging go.Volume: Loud enough to hear even with hearing protection on. Volume is non-adjustableThreshold: Adjustable in the menu.
Verified Purchaser · June 10, 2 · ✓ Amazon Verified Purchase
★★★★★
Very useful to have
First of all, I'd like to say how happy I am with how well this was packaged. It showed up in good shape and undamaged, and all the parts I'd use were still in the packaging. It was easy to set up and use because the instructions were clear and simple, which is a bonus if you know what I mean. And I'm sure you do. The screen's big enough to read easily. The buttons work like you're supposed to, and I'm really pleased with it. Excellent value for the money. Good job, people.
Verified Purchaser · June 22, 2 · ✓ Amazon Verified Purchase
★★★★★
Well made, super compact
Search for a gas detector led me here. Brand name didn't matter; quality, safety and functionality did. Below are the features that attracted me to this particular one.4 Gas Monitor, Mini & Small, USA NIST Calibration, O2, CO, H2S, LEL, Detection, USB Recharge• Brand: FORENSICS DETECTORS FD• Style: Modern• Power Source: Battery Powered• Color: Yellow• Product Dimensions: 2.6"D x 1.2"W x 5.1"H• Item Weight: 0.6 Pounds• SENSOR: High-quality nano sensors, 4-gas meter detects - Oxygen (O2), carbon monoxide (CO), hydrogen sulfide (H2S), and combustibles (LEL); FACTORY-CALIBRATED• DETECTION: Ultra advanced nano-sensors, high fidelity, resolution• ALARMS: Adjustable audio, visual, vibration alarms• STRONG: Rubber feel, high-strength ABS anti-slip grip; water-resistant, dust-proof, explosion-proof• TRUSTWORTHY: 1-year limited warranty, calibration + QA certificates included; USA tested, verified• EASY TO USE, COMPACT & ULTRA PORTABLE: Easy to use, simple, reliable, remarkably compact - one of the smallest 4-gas monitors in the world; cutting-edge personal protection, advanced electrochemical + catalytic nano-sensors, ultra-portable design for confined space air assessment; no complicated menus, no unnecessary features• What's in the box: 4 gas monitor, english manual, USB charging cable, calibration cover, metal belt clip, NIST calibration certificate• Small Business: This product is from a small business brand. Support small.Overall, this ultra portable, compact 4-Gas Monitor met my expectations for all the features listed above and represents a good value for me. I got this for peace of mind and protection. We have gas appliances as well as utility digging beind our house, so natural gas leaks and compromised air quality are a possibility.This is a solid, well made, ultra-portable tool with a 2-3 year sensor life. The display is easy to read, the handle is comfortable and the audible/vibrating alarms are appreciated. It is engineered for industrial use by utility workers and firefighters, so we have confidence in its results. With USA NIST Traceable Source Calibration, we also have the highest confidence in our gas detection accuracy and safety.There is an easy to follow user guide included. Happy to find and recommend this affordable quality necessity that supports small business.
Verified Purchaser · March 14, · ✓ Amazon Verified Purchase
★★★★★
Compact 4 Gas Meter With Clear Alarms
This 4 gas meter is a compact safety tool for monitoring O2, CO, H2S, and LEL levels in areas where air quality matters. The size is small enough to clip to a belt or vest without getting in the way, and the rubberized ABS housing gives it a durable grip for field or shop use. The display is easy to read, the controls are simple, and the alarms are hard to miss with sound, light, and vibration alerts. I like that it arrives calibrated with certificates included, along with the manual, USB charging cable, calibration cover, and belt clip. The rechargeable battery is convenient, although I would still keep it charged before any serious use instead of assuming maximum runtime. Overall this is a well made portable gas detector with good safety features, easy operation, and good value for the money compared to higher priced gas meters.
Verified Purchaser · May 9, 202 · ✓ Amazon Verified Purchase
★★★★★
Excellent quality device for personal safety
This is an exceptionally good quality 4-gas meter with multiple alarm options. Weighing just under 5 ounces, it can be clipped onto my belt or vest so I can continuously monitor the surrounding gas levels for my personal safety. The highly sensitive nano sensors can detect the levels of 4 gasses: Oxygen (O2), Carbon Monoxide (CO), Hydrogen Sulfide (H2S), and Combustibles (LEL). It arrives fully calibrated and calibration certificates are provided. It has just 3 buttons which I found easy to use and it has a clear backlit digital display. The thresholds can be adjusted for each gas as needed. If the preset warning limits are exceeded, the unit produces sound, light, and vibration alarms to alert me. The unit is well-made of tough ABS and feels very durable. It has been well-designed to wear in hazardous environments and is water-resistant, dust-proof, and explosion-proof. It comes with a 2000mAh Li-ion battery and the charging block and cord were provided.
Verified Purchaser · May 5, 202 · ✓ Amazon Verified Purchase
★★★★★
Great Deal!
Handy gadget for those wanting to do some quick checks around the house! Gives you the peace of mind that your house is safe, and definitely gets the job done without the typical cost of a professional inspection - but please, if you actually believe there is a problem DON’T HESITATE to do the in person inspection! All in all this is a great option for over time maintenance checks, testing homes before purchasing, or any “just in case” scenarios.
Verified Purchaser · May 15, 20 · ✓ Amazon Verified Purchase
Showing 8 of 23 Amazon reviews.
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