WatchGas SST4 MINI Diffusion Bundle

Six components in one order:

• WatchGas SST4-MINI Diffusion 4-Gas Detector — monitors LEL, O2, CO, and H2S continuously, with your choice of LEL CAT or LEL NDIR sensor variant
• PK Safety WatchGas Equivalent Calibration Kit (PKCalKit-WG) — automatically discounted $50 when purchased in this bundle
• 34-liter 4-gas calibration gas cylinder matched to the SST4 MINI's sensor set (LEL / O2 / CO / H2S)
• Fixed flow regulator at 0.5 LPM — matches the SST4 MINI's diffusion calibration flow rate
• 1 foot of Tygon tubing for the calibration connection
• Padded carrying case (ISG C-100) that keeps all components together for field or truck-bed storage

Everything a crew needs to stand up four-gas confined-space monitoring on the day the bundle arrives.

The bundle saves $50 on the calibration kit (auto-applied at checkout) and delivers everything in one shipment. Buying components separately is worth it only if:

• You already own some of the components (an existing calibration kit, regulator, or cylinder that fits the SST4-MINI's diffusion calibration requirement)
• You need a different gas mix than the standard 4-gas (LEL / O2 / CO / H2S) — for example, a five-gas mix that adds a specialty toxic like SO2 or NH3
• You need a different regulator flow rate than 0.5 LPM (for example, the SST4-PUMP variant needs a different calibration setup)
• You're already running a calibration workflow at a facility and only need the monitor itself

For new safety programs, temporary contractors, mutual-aid teams, and any buyer standing up a confined-space monitoring capability from scratch, the bundle is faster to receive and simpler to deploy than sourcing components across multiple suppliers.

LEL CAT (Catalytic Bead) is the safety industry's standard combustible-gas sensor. It burns a small amount of gas across a heated bead and measures the temperature change. It detects any flammable hydrocarbon vapor and it detects hydrogen. Two caveats: catalytic beads can be poisoned by silicones (found in some caulks, lubricants, cleaners, and mold-release compounds) and their calibration can drift after prolonged H2S exposure. Bump testing catches these drifts, but the sensor is more vulnerable to environmental contaminants than NDIR.

LEL NDIR (Non-Dispersive Infrared) uses an infrared beam and a detector to measure hydrocarbon absorption. It's immune to silicone poisoning and H2S-induced calibration drift, which makes it the better choice for oil and gas upstream/downstream work, refineries, and any confined-space environment with sour hydrocarbon exposure. One tradeoff: NDIR does not detect hydrogen. If your confined-space program requires hydrogen alarming alongside the standard four gases, LEL CAT is the right choice.

The $100 price difference between the two bundle variants is the sensor upgrade. If you're doing petroleum or petrochemical work, the NDIR upgrade usually pays for itself in reduced nuisance alarms and calibration drift over the monitor's service life.

The 34-liter calibration gas cylinder in the kit is classified as HazMat under U.S. Department of Transportation (DOT) regulations. HazMat air shipping requires special certifications, packaging, and cost premiums that would double or triple the bundle's landed cost. UPS Ground is the compliant, cost-effective shipping method for this product.

If you need faster delivery of the monitor and can wait on the calibration kit, you can order the SST4-MINI detector separately (not a HazMat item) and have the calibration kit arrive on Ground timing. Call PK Safety at 800.829.9580 to arrange a split shipment.

The industry standard for portable gas monitors in confined-space service is to bump test before each use (a quick verification that each sensor responds to gas) and to full-calibrate every 3 months (a precise measurement of sensor response against the cal gas standard).

OSHA's confined-space standard 29 CFR 1910.146 does not mandate a specific calibration frequency, but the industry consensus and manufacturer guidance point to the 3-month interval for accuracy assurance and audit-log completeness. Both procedures use the calibration components in this bundle: the 34-liter cal gas cylinder, the 0.5 LPM regulator, and the Tygon tubing.

See How Often Do I Need To Calibrate My Monitor? for full detail on bump testing and calibration frequency.

Yes. OSHA's permit-required confined spaces standard 29 CFR 1910.146 requires atmospheric testing before entry for oxygen content, flammable gases (measured as % LEL), and toxic gases (typically CO and H2S in industrial contexts). The SST4-MINI in this bundle continuously monitors all four of those parameters, and the included calibration kit provides the workflow to verify sensor accuracy at industry-standard intervals.

For confined-space programs that need additional gases beyond LEL / O2 / CO / H2S — for example, SO2 at refineries or NH3 at food and beverage plants — a separate single-gas monitor from the WatchGas SST1 line is the right complement to the SST4-MINI in this bundle.