Client Background
The client required confirmation that a specialist hazmat suit was suitable for use in operations involving flammable dusts and solvents.
Their current Hazmat suit was made from insulating plastic materials, which, in theory, could accumulate electrostatic charge during use. Producing either a brush or spark discharge and ignite a flammable atmosphere.
Client Problem
The key concern was whether the insulating properties of the suit could lead to charge build-up and an in turn, an incendive electrostatic discharge.
The client needed clarity on:
- Whether the suit and associated gloves could be used safely in flammable vapour, gas, or dust atmospheres.
- Whether additional layers or operational controls were required to make the suit suitable for hazardous area use.
To address these questions, a Charge Transfer test methodology, referenced in standards such as BS EN ISO 80079-36 was selected.
Client Objectives
The client sought a definitive assessment outlining:
- The electrostatic discharge behaviour of the suit under test and in realistic operating conditions.
- Suitability for use within specific hazardous zones and explosion groups.
- Any control measures or additional PPE required to ensure safe operation.
Insights
Charge Transfer Approach
The standard test conditions alone did not adequately represent real-world usage. To produce a meaningful assessment, Sigma-HSE adapted the standard methodology to include:
- Using a mannequin coated in earthed, aluminium foil to simulate a human operator electrically conductive nature.
- The hazmat suit was donned onto the mannequin, and discharge measurements were performed during simulated movement, where the suit was allowed to fall away from the body, potentially generated higher levels of charge than the standard test method would indicate.
Testing was repeated with a Tyvek under-layer between the mannequin and the suit to further replicate typical operator attire and more realistic charge-transfer pathways.
Findings
- Measured discharges from the suit visor and black outer gloves indicated that, without a Tyvek layer, the Hazmat suit posed a risk of incendive discharge in flammable vapour or gas atmospheres within Zone 0 or Explosion Groups I, IIA, IIB, or IIC.
- With a Tyvek suit worn underneath, testing suggested potential suitability for Explosion Group IIA atmospheres in Zones 1 & 2 only.
Outcomes
Sigma-HSE determined that:
- With no Tyvek underlayer: the Hazmat suit and outer gloves should not be used in flammable gas or vapour atmospheres.
- With a Tyvek underlayer: the suit may be suitable for use in Explosion Group IIA, Zones 1 & 2, based on observed discharge characteristics.
- For flammable dust atmospheres for which brush discharges are not incendive, the suit was deemed suitable provided that conductive tools, containers, or equipment handled by the operator are securely and independently earthed.
The testing provided the client with a clear, evidence-based understanding of how the suit behaves electrostatically and under what specific conditions it can be safely used or should not be used.
