Chemical exposures get most of the attention, but many workplace risks are physical: heat, ultraviolet light, ionising radiation and vibration. Measuring them needs purpose-built instruments, because each hazard is defined by an index or quantity that ordinary meters do not report. Respiratory protection belongs alongside them, because a respirator only works if it actually seals to the wearer's face.
Heat Stress: WBGT
Air temperature alone does not describe heat strain. Humidity limits sweat evaporation, radiant heat from sun, furnaces or hot surfaces adds load, and air movement helps cooling. The wet bulb globe temperature (WBGT) index combines these through three sensors:
- Natural wet bulb (Tnw) — responds to humidity and air movement;
- Black globe (Tg) — responds to radiant heat;
- Dry bulb air temperature (Ta).
Under ISO 7243, indoors or without solar load, WBGT = 0.7 Tnw + 0.3 Tg. Outdoors in sunshine, WBGT = 0.7 Tnw + 0.2 Tg + 0.1 Ta. The result is compared with reference values that depend on metabolic rate and acclimatisation, and it guides work–rest schedules.
MEWOI's WBGT monitors use Pt1000 sensors and replaceable 50 mm or 150 mm black globes, with a built-in humidity sensor and RS-485 output. The WBGT2019A uses a conventional water-fed wet bulb; the WBGT2019B uses a waterless wet bulb sensor for long-term unattended monitoring.
Ultraviolet Radiation
UV exposure comes from the sun, welding arcs, curing systems and germicidal lamps. The relevant band depends on the source: UVA (315–400 nm) and LED "UVV" around 395 nm for curing, UVB (280–315 nm), and UVC (100–280 nm) for germicidal lamps at 254 nm. A UV radiometer measures irradiance in a defined band, so the probe must match the source.
The MEWOI-SD2040 takes interchangeable digital probes for UVV (peak 395 nm), UVA (365 nm), UVB (297 nm) and UVC (254 nm), which it identifies automatically. It also integrates irradiance to dose in mJ/cm² for curing and disinfection checks. Assessing exposure against occupational limits needs a spectrally weighted measurement, so use an instrument designed for hazard assessment where that is the goal.
Ionising Radiation
Industrial radiography, X-ray equipment, nuclear gauges and some scrap and building materials can expose workers to gamma and X-radiation. A personal dosimeter with a Geiger–Müller detector shows the dose rate in real time, accumulates dose and alarms at set thresholds. That alarm is the main protection for people working near sources.
The MEWOI-RG600 and RG1000 use energy-compensated GM tubes for X, gamma and hard beta radiation, with adjustable dose-rate and cumulative-dose alarms, sensor-fault indication and memory that survives power loss. Electronic alarming dosimeters supplement, rather than replace, the formal dosimetry a radiation licence may require.
Vibration: Machines and People
Vibration meters serve two different purposes:
- Machine condition: vibration velocity (mm/s RMS) on bearing housings is compared against severity guidance — historically ISO 2372, now the ISO 10816/20816 series — to judge the condition of rotating machinery.
- Human exposure: hand-arm vibration from tools and whole-body vibration from vehicles are measured as frequency-weighted acceleration (m/s²), following ISO 5349 and ISO 2631, with instruments built to ISO 8041.
MEWOI's vibration meters span both. The supplier states that the HS5944 pocket meter reads acceleration, velocity and displacement for machine assessment to ISO 2954; the HS5936 adds hand-transmitted vibration weighting; and the HS5933A environmental analyser applies whole-body weightings to ISO 8041 type 2 and records statistical vibration levels.
Respirator Fit
A tight-fitting respirator's rated protection depends on the face seal. Quantitative fit testing compares particle concentration outside and inside the facepiece while the wearer performs a set of exercises. The ratio is the fit factor, which must reach the minimum for that respirator class. Workplace health and safety rules, and AS/NZS 1715 in Australia, call for fit testing of tight-fitting respirators.
The AccuFIT 9000 supplied by MEWOI uses condensation particle counting of ambient particles from 0.02 to 1.0 µm. It has built-in OSHA, CSA, ANSI/AIHA and HSE protocols, and one PC can run up to four testers.
Frequently Asked Questions
Can I calculate WBGT from a weather forecast? Estimates exist, but radiant heat and air movement at the workplace vary a great deal. On-site measurement is more reliable, especially near hot processes.
Is a qualitative fit test acceptable? For some half-face respirators, yes. Full-face respirators and higher protection factors typically need quantitative testing. Check the requirements that apply to your workplace.