Food Trailer & Food Van Exhaust Certification, Perth WA

01What the check finds

Four things that stop a trailer being certified.

A trailer’s exhaust usually looks right. Whether it is right comes down to four things the check measures, each with a clause behind it.

Airflow

The fan is rated at free air.

Small axial fans are rated with nothing in front of them. Put filters in front and the real airflow falls, usually below what the hood needs. A fan mounted inside the hood also puts its motor in the grease stream.

Filters

The filters are mesh, and too flat.

AS 1668.2 wants filter faces vertical or within 30° of vertical, so grease drains instead of dripping, and every filter working inside its maker’s flow and temperature limits. Unrated aluminium mesh has no limits to check, and some council guidelines ask for baffle filters listed to UL 1046.

Clearance

Open burners sit too close.

The lowest edge of the filters has to be 1050 mm above an open flame, or 600 mm above an electric appliance or a fixed plate or pan over gas. Inside a trailer about 2 m high, 1050 mm rarely fits. A flat plate or an electric hob usually does.

Grease

Nowhere for the grease to go.

A low sidewall hood may drain to a removable container, but it has to have one, with a channel feeding it. Some council guidelines also ask for a light that shows the fan is running.

02A compliant trailer

Fan, filters, clearance, air, distance.

A cross section through a typical food trailer, and the five things that have to be right for the exhaust to be certified.

Cross section of a food trailer: a low sidewall hood over the cooking line with baffle filters within 30 degrees of vertical, a duct through the roof to a fan with vertical discharge, make-up air entering through the serving window, the filter clearance above the cooking surface, and the 2 m separation from the outlet to the serving window — 1
**Roof fan, vertical discharge.** Sized on the airflow measured through the filters, not on the supplier’s free-air figure, and fixed for wind and towing.

2
**Baffle filters within 30° of vertical.** Each inside its maker’s limits, draining through a channel to a removable container.

3
**Filter to cooking surface.** At least 600 mm above a plate, pan or electric appliance; 1050 mm above an open flame.

4
**The serving window is the make-up air.** It stays open by a set minimum while cooking, and a window beside the fryer stays shut so a cross-draught cannot pull smoke out of the hood.

5
**Distance from the outlet.** Under 400 L/s, at least 2 m from any intake, natural ventilation device or opening. Above that the distance grows, one more reason to get the airflow right rather than big.

03The airflow

The method decides whether the trailer is possible.

AS 1668.2-2002, the edition several WA council guidelines still name, gives two ways to set the exhaust airflow. The prescriptive route multiplies the hood length by a factor for the hardest-working appliance under it. The other route, intended for several appliances sharing one hood, rates each appliance on its own cooking surface and its own process type.

On a recent trailer the prescriptive route asked for about four times the air of the cooking-surface route. Four times the air means a bigger fan on the roof, more air pulled through the serving window, and a discharge that has to sit further from every opening. The cooking-surface route gave a fan that fits and an outlet that keeps its distance.

That is the decision most worth getting right. Under 400 L/s, the Standard asks for 2 m between the outlet and any intake, natural ventilation device or opening, and that band is what makes a compliant trailer workable.

04The council’s guideline

When a fixed-kitchen rule meets a trailer.

Council hood guidelines are written for fixed kitchens. Several add a hood lower edge 2 m above the floor, a discharge 3 m above a flat roof, and 6 m from boundaries and air intakes. A trailer about 2 m high inside, under a 4.3 m road height limit, cannot meet those literally.

The answer is not to ignore them. It is to list each one, show what AS 1668.2 itself allows, and ask the council to accept it in writing before anything is fabricated. Fabricating first and asking afterwards is how a trailer gets built twice.

05Scope

What you get.

Site visit: the hood, filters, fan, appliances, windows and gas measured and photographed
Assessment report, clause by clause: what was found and whether it complies
A straight answer on whether the existing system can be certified as it is
The smallest set of changes that makes it comply, keeping what can be kept
Airflow by the route that suits the trailer, with the fan duty and the filter basis
Written requests for the council’s acceptance where its guideline cannot be met literally
Review of the fabricator’s shop drawing and the fan and filter selections before work starts
Commissioning: airflow measured with a calibrated anemometer, smoke capture checked, fan speed locked
Written certification listing the installed fan and filters, the measured airflow and the operating conditions
A short note of what the owner keeps doing: filters cleaned, window open, fan on whenever cooking

06Process

From the council’s letter to a certificate.

Send what you have
The council’s letter, and photos of the hood from below, the fan, the filters, the cooking line and the windows.
Scope and fixed fee
A short call, then a fixed fee for the visit and the report. If the trailer clearly cannot work as it is, you hear that first.
Site visit
Everything measured and photographed: the hood, the filters and their angle, the fan, the clearances, the windows and the gas.
Report to the council
The assessment, the proposed fix and the acceptance requests, written for the environmental health officer to read.
The work
Your fabricator, gasfitter and electrician build to the reviewed drawing. Questions answered while they do.
Commission and certify
Airflow measured, capture checked with smoke, fan speed locked, certification in writing.

07How we work

Clear on who does what.

I assess, design and certify the kitchen exhaust to AS 1668.2 as a mechanical engineer (MIEAust NER). Gas work is installed and certified by a licensed gasfitter, and electrical work by a licensed electrician. The council decides whether to accept the design and the certificate, which is why the acceptance requests go to them before anything is built.

If the existing system can be certified with small changes, you hear that. If it cannot be certified as it stands, you hear that first, before you spend money on parts.

Typical clients: food trailer and food van owners with a letter from the council, people buying or selling a used trailer who want to know where it stands, and fabricators building new ones. For fixed commercial kitchens, see kitchen exhaust and ventilation design.

08Questions

What trailer owners ask.

The council wants my food trailer exhaust certified to AS 1668.2. What does that involve?

A site visit to measure the trailer and its exhaust, a clause by clause check against the edition of AS 1668.2 the council names, and the smallest set of changes that makes it comply. Where the council's own hood guideline cannot be met on a trailer, its written acceptance is requested before anything is built. After the work is done, the system is commissioned with the airflow measured, and the certification is put in writing.

Can my existing exhaust fan be kept?

Only if it delivers the required airflow with the filters fitted. Small axial fans are usually rated at free air, with nothing in front of them, and deliver less once filters are installed. A fan mounted inside the hood also puts its motor in the grease stream.

Do I need a 3 m stack on my food trailer?

AS 1668.2-2002 sets no stack height for a kitchen discharge under 1000 L/s. Some council guidelines add 3 m above a flat roof, which a trailer cannot meet under the 4.3 m road height limit. The usual answer is a vertical discharge above the roof, at least 2 m from any opening when the exhaust is under 400 L/s, and a written request for the council to accept it.

Can I keep the open gas burners?

Only if the grease filters sit at least 1050 mm above them, which inside a trailer about 2 m high is rarely possible. A flat plate over gas, or an electric hob, needs 600 mm, which usually fits.

Who certifies the gas and electrical work?

A licensed gasfitter certifies the gas installation and a licensed electrician the electrical work. The exhaust certification covers the ventilation to AS 1668.2.

Food Trailer Exhaust, WA