Ventilation, stair pressurisation and exhaust contractor and consultant —code-compliant mechanical ventilation

Hiring a ventilation, pressurisation & exhaust contractor — what to check

Industrial ventilation is bought in two very different forms and the terms get used interchangeably, which is how factories end up with the wrong one. General ventilation dilutes the whole shop. Local exhaust captures the contaminant at the source. A fume problem solved with more air changes is usually a fume problem moved, not solved.

• Capture velocity at the hood, not air changes in the shed. For fume, dust or solvent extraction the number that matters is the velocity at the point of capture and the hood geometry that achieves it. Air changes per hour is the wrong specification for a source-capture problem.
• Make-up air, costed honestly. Every cubic metre extracted has to be replaced. A system designed without tempered make-up air either starves, pulls the shed into depression, or drags your heating and cooling cost up. It is the most commonly omitted line in a cheap quote.
• What the pollution board consent requires. Stack height, monitoring provision and any scrubber or filtration are conditions of your consent, not optional refinements. The design has to be the consent's design.
• Balancing and the report. Measured airflows at each hood and outlet against the design, issued as a balancing report. Without it nobody can say whether the system works.