Explosion Proof Scales: Hazardous Location Scale Buyer’s Guide
Reviewed by MNM Scales technicians · Updated October 31, 2026 · Prices checked October 31, 2026
Short answer: an explosion proof scale is any scale approved to work where flammable gas, vapor or dust can be present. For weighing in Class I, Division 1 areas, most plants use intrinsically safe battery scales because there is no barrier or conduit to install. For pails, bags and drums, the A&D HW-60KCEP ($1,864, 150 lb x 0.01 lb) up to the HW-200KCEP ($1,998, 500 lb x 0.05 lb) are approved for Class I, Division 1, Groups C and D, T4. For additives and samples, the A&D EK-3000AEP ($1,089, 3000 g x 0.1 g) carries the same Class I, Division 1 approval. For floor, drum and crane systems, send us your area classification and we will quote a matched system.
Refineries, petrochemical units, tank farms and paint and coatings plants all have spots where a spark or hot surface could ignite the air. Any scale used there has to carry an approval that matches the area. MNM Scales has supplied, calibrated and repaired scales for over 30 years. From our Cypress, Texas shop we serve oil, gas and chemical plants along the Houston Ship Channel and across Texas. This guide explains the protection methods behind the words explosion proof and intrinsically safe. It also covers how Class, Division and Zone markings work, when you need a safety barrier, and which bench, floor, drum and crane options fit each job. For lab balances and chemical batching outside classified areas, see our chemical weighing scale guide.
Explosion proof scale or intrinsically safe: what the terms mean
Buyers say explosion proof for any hazardous-location scale, but the approval label names one of several protection methods. Each one prevents ignition in a different way:
| Protection method | How it works | Typical marking | Common scale use |
|---|---|---|---|
| Explosion proof (flameproof) | A heavy enclosure contains any internal explosion and cools escaping gases so they cannot ignite the area | XP; Ex d in the zone system | Indicators, junction boxes and motors wired in conduit |
| Intrinsically safe | Circuits run on so little energy that a spark or hot surface cannot ignite the gas | IS; Ex ia or Ex ib | Battery bench scales, balances, load cells wired through barriers |
| Purged and pressurized | Clean air or inert gas keeps the enclosure at positive pressure so the gas stays out | Type X, Y or Z; Ex p | Larger indicators, printers and PCs |
| Nonincendive (Division 2 only) | Equipment does not produce an igniting spark or temperature in normal operation | NI; Ex n or Ex ec | Division 2 and Zone 2 areas |
Intrinsic safety is the usual choice for scales because the platform, load cell and display can sit right where the work happens. A battery-powered intrinsically safe scale needs no wiring at all, so you can carry it between units and use it the day it arrives.
Class, Division and Zone: reading a hazardous location scale label
- Class names the hazard: Class I is flammable gas or vapor, Class II is combustible dust such as flour, sugar, grain, plastic or metal powder, and Class III is ignitable fibers.
- Division names how often it is there: Division 1 means it can be present in normal operation, Division 2 means only under abnormal conditions such as a leak.
- Zone is the alternative system used under NEC Article 505 and internationally: Zone 0 has gas present continuously, Zone 1 in normal operation and Zone 2 only abnormally.
- Group names the gas. Group D covers propane, gasoline, acetone, methanol, hexane and toluene; Group C covers ethylene and diethyl ether; Group B is hydrogen; Group A is acetylene. In the zone system, IIA and IIB match Groups D and C, and IIC covers hydrogen and acetylene.
- Temperature code is the highest surface temperature: T3 is 200 °C and T4 is 135 °C. It must stay below the ignition temperature of the gases in the area.
Equipment approved for Division 1 can also be used in a Division 2 area of the same class, group and temperature code, and Zone 0 equipment can be used in Zones 1 and 2. That is why a Division 1 intrinsically safe scale is a flexible choice for plants with both kinds of areas. For Class II dust areas or Group A and B gases, send us your classification and we will source a scale approved for them.
Intrinsically safe bench scales and balances in stock
A&D HW-CEP bench scales: 150 to 500 lb
The HW-60KCEP ($1,864, 150 lb x 0.01 lb, 13.0 x 16.7 in platform), HW-100KCEP ($2,099, 200 lb x 0.02 lb) and HW-200KCEP ($1,998, 500 lb x 0.05 lb) handle bags, pails and drums at sample points, filling stations and loading racks. The A&D manual lists these approvals:
- FM (US): Intrinsically Safe Class I, Division 1, Groups C and D, T4, and Class I, Zone 0, AEx ia IIB T4
- IECEx and ATEX: Ex ia IIB T4 Ga, ambient -25 to +40 °C
- Power: four D-size alkaline batteries (not included) of the brands named in the manual: Duracell MN1300, Energizer E95 or Panasonic LR20(XJ)
- Build: IP65 platform, 1/10,000 resolution and a 3-color comparator for filling to a target weight
Source: A&D HV/HW-CEP series page and instruction manual.
A&D EK-AEP balances: 300 g to 12 kg
The EK-300AEP ($1,015, 300 g x 0.01 g), EK-3000AEP ($1,089, 3000 g x 0.1 g) and EK-12KAEP ($1,349, 12 kg x 1 g) weigh tints, additives, catalysts and samples where they are mixed. A&D lists FM Intrinsically Safe Class I, Division 1, Groups C and D, T3C, and Ex ia IIB T3 Ga for IECEx and ATEX. They run on four AA alkaline batteries (not included): Duracell MN1500, Energizer E91 or Panasonic LR6(XJ), as named in the manual. Source: A&D EK-AEP product page and EK-AEP instruction manual (PDF).
Sending weights to a PC or control room
The EK-AEP balances send data as light through an optical fiber cable to the A&D AD-1611 optical adapter (both sold separately, not included). The adapter is installed in the non-hazardous area, so no electrical signal crosses the boundary. For more on displays and outputs, see our scale indicator buying guide.
Intrinsically safe barriers for wired scale systems
A wired system, such as a floor scale or tank load cells in the classified area with the indicator or PLC outside, needs an intrinsically safe barrier at the boundary. The barrier limits the voltage and current that can reach the field wiring, even if something fails on the safe side.
- Zener barriers divert excess energy to a dedicated intrinsic safety ground, so they need a low-resistance ground connection.
- Galvanic isolators separate the two sides with transformers or optocouplers, so they work without that dedicated ground and suit many retrofit jobs.
- Entity parameters confirm the match: the barrier’s output voltage, current and power must be within what the load cells and indicator accept, and the cable’s capacitance and inductance count toward the totals.
- The control drawing from the scale or load cell maker shows the approved barriers and wiring. Installation follows NEC Article 504 for intrinsically safe systems.
Send us the area classification, the distance from the scale to the safe area and where the weight needs to go, and we will spec the load cells, barriers and indicator together.
Bench, floor, drum and crane options by plant area
| Where it is used | Typical job | What to choose |
|---|---|---|
| Unit sample points and labs inside the fence | Weighing samples, catalysts and additives | EK-300AEP, EK-3000AEP, EK-12KAEP |
| Paint and coatings mixing rooms | Tinting, solvent and resin additions by weight | EK-12KAEP for tints, HW-60KCEP for pails |
| Drum filling and pail lines | Filling to a target weight | HW-100KCEP or HW-200KCEP with the built-in comparator |
| Loading racks, tank farms and warehouses with totes | Drums, totes and pallets over 500 lb | Intrinsically safe floor or drum scale built to order; see floor scales |
| Process vessels and hoppers | Tank and hopper weighing | Load cells with matched barriers and an indicator in the safe area |
| Maintenance and lifting | Weighing loads on a hoist | Hazardous-area crane scale quoted to your classification; see crane scales |
Floor and drum systems use the same platform choices as any floor scale, with approved load cells, barriers and an indicator that fits the area. For a stainless indicator on a platform system, see the MNM Scales XK3150-EX explosion proof indicator ($998), with RS-232C, counting and hold functions. Send your area classification with the order and we will confirm the marking fits. For lifting, our crane scale guide covers capacity and readability.
Compare explosion proof scales in stock
| Scale | Capacity x readability | Hazardous-area approval | Best for | Price |
|---|---|---|---|---|
| A&D EK-300AEP | 300 g x 0.01 g | FM Class I Div 1, Groups C, D, T3C; Ex ia IIB T3 Ga | Samples | $1,015 |
| A&D EK-3000AEP | 3000 g x 0.1 g | FM Class I Div 1, Groups C, D, T3C; Ex ia IIB T3 Ga | Additives and tints | $1,089 |
| A&D EK-12KAEP | 12 kg x 1 g | FM Class I Div 1, Groups C, D, T3C; Ex ia IIB T3 Ga | Small batches | $1,349 |
| A&D HW-60KCEP | 150 lb x 0.01 lb | FM Class I Div 1, Groups C, D, T4; Ex ia IIB T4 Ga; IP65 | Bags and pails | $1,864 |
| A&D HW-100KCEP | 200 lb x 0.02 lb | FM Class I Div 1, Groups C, D, T4; Ex ia IIB T4 Ga; IP65 | Pails and small drums | $2,099 |
| A&D HW-200KCEP | 500 lb x 0.05 lb | FM Class I Div 1, Groups C, D, T4; Ex ia IIB T4 Ga; IP65 | Drum filling | $1,998 |
Using and caring for a hazardous location scale
- Change batteries outside the classified area and use alkaline batteries of the brands named in the manual; they are part of the approval.
- Clean with a damp cloth. A dry cloth can build static. The HW-CEP base can take gentle running water; protect the display unit from dust and water.
- Ground the scale where static electricity may build up, using the grounding screw hole described in the manual (grounding wire not included).
- Keep the scale as built. A&D instructs users to leave the scale unopened and unmodified, so send it to us for service.
- Recalibrate after moving the scale to a new location, and check it daily with a known weight.
Rules: when a hazardous-area scale must be legal for trade
Weighing for your own process, blending and inventory is process weighing. Once a price, invoice or shipping charge depends on the weight, the scale is used in trade and must meet NIST Handbook 44. TDA does not require an NTEP certificate for every device, but the scale must meet NIST Handbook 44 and suit its use; some scales do need one, so we recommend NTEP models and can check yours. TDA explains this in Legal for Trade Scales in the State of Texas (PDF).
- If a hazardous-area scale will be used to sell or invoice by weight, tell us when you order so we can match a model with the approvals your use needs. Learn more in what NTEP legal for trade means.
- In Texas, our TDA-registered technicians can calibrate and place a commercial scale in service. See legal-for-trade calibration in Texas and our TDA scale certification guide.
- Check a scale with the free Texas legal-for-trade scale checker, or see how far a reading may drift with the scale tolerance calculator.
Calibration for explosion proof scales
Safety and quality programs usually ask for calibration on a set schedule with a certificate. Every scale above can ship calibrated; the tier depends on maximum capacity.
| Capacity | Models | In-house + certificate | NIST + certificate |
|---|---|---|---|
| Up to 2.2 kg | EK-300AEP | $95 | $395 |
| 2.2 to 6.2 kg | EK-3000AEP | $195 | $495 |
| 6.2 to 35 kg | EK-12KAEP | $250 | $595 |
| 35 to 150 kg | HW-60KCEP, HW-100KCEP | $350 | $750 |
| Over 150 kg | HW-200KCEP, floor and drum systems | $495 | $995 |
- On-site service: $295 + $2 per mile per visit across the Houston area, with calibration charged per scale, including plants in Pasadena and Baytown, Deer Park and La Porte, Channelview and Texas City. Tell us the area classification and your site safety requirements when you book. Our technicians bring their own test weights for floor scales. On-site calibration details.
- Plant scales: see industrial scale calibration in Houston.
- Mail-in calibration: ship bench scales and balances to us from anywhere. How mail-in calibration works.
- Check weights: keep one for daily checks; see calibration weights (not included with scales).
- Repairs: we repair the brands we sell.
Scale rentals
Need a scale for a turnaround or a short project? MNM rents all types of scales. Call (832) 290-3120 or request a quote with your area classification.
Need an explosion proof scale quoted? Send us the area classification (class, division or zone, group and temperature code), what you weigh, the capacity and readability, and where the weight needs to go. We will recommend a scale or system, quote calibration, and have it ready to ship or for pickup in Cypress.
Frequently asked questions
What is an explosion proof scale?
It is a scale approved for use where flammable gas, vapor or dust can be present. Strictly, explosion proof is one protection method, a sealed enclosure that contains an internal explosion. Most hazardous-area scales use intrinsic safety instead, which keeps circuit energy too low to ignite the area.
Is an intrinsically safe scale the same as an explosion proof scale?
Both are approved for hazardous locations but they work differently. An explosion proof enclosure contains an ignition, while an intrinsically safe scale cannot create one. For bench scales and balances, intrinsic safety is the usual choice because the scale stays light and portable.
Do I need an intrinsically safe barrier?
Battery-powered scales such as the A&D EK-AEP and HW-CEP need no barrier. Wired systems, such as a floor scale or tank load cells in the classified area with the indicator outside, need a barrier or galvanic isolator that matches the control drawing.
Can a Division 1 scale be used in a Division 2 area?
Yes. Equipment approved for Division 1 can be used in a Division 2 area of the same class, group and temperature code, and Zone 0 equipment can be used in Zones 1 and 2.
Which gases are the A&D intrinsically safe scales approved for?
The EK-AEP balances and HW-CEP bench scales are approved for Class I, Division 1, Groups C and D, which include propane, gasoline, acetone, methanol, hexane, toluene and ethylene. The HW-CEP is rated T4 (135 °C) and the EK-AEP T3C (160 °C).
Do you have explosion proof floor and crane scales?
Yes, we quote floor, drum, tank and crane systems to your area classification, gas group and capacity, with approved load cells, barriers and indicators. Call (832) 290-3120 or request a quote.
Can MNM Scales calibrate scales in a classified area?
Yes. On-site service is $295 + $2 per mile per visit across the Houston area, with calibration charged per scale. Tell us the area classification and site safety requirements when you book. MNM rents all types of scales if you need one while yours is serviced.