// safety

Safety first, or not at all.

Biogas is flammable, and it pushes the air you breathe out of the way. Anyone can build a digester — but only by following these rules without exception.

// the non-negotiables

Eight rules we do not bend.

These apply to every FRSH build: a jar on a windowsill, a drum in a school yard, or a pilot run with a university lab.

  1. Sealed systems only. Gas is collected, never left to collect in a room.
  2. Outdoors, or in a ventilated shed. Never a bedroom, a basement, or a garage joined to living space.
  3. No flame, no spark, no smoking. Keep the digester and its gas line away from cookers, heaters and switches.
  4. No pressurised storage. Gas is held at near-atmospheric pressure, or it is not held at all.
  5. A named adult is responsible. Anyone under 18 works supervised, and that adult's name is on the build.
  6. Gloves and eye protection whenever you handle feedstock or digestate.
  7. Never open a working digester to look inside. Keep the water trap in place.
  8. Stop at the first doubt. A strong gas smell, damaged tubing, or feeling unwell means stop, leave, and tell your supervisor.
// why it bites

Two ways biogas hurts people.

Fire

Methane catches fire easily

Methane burns across a wide range of mixtures with air, and biogas also carries hydrogen sulfide, which is toxic. A leak beside a flame is a fire before you have time to react.

Air

It pushes the oxygen out

In a closed space, methane and carbon dioxide displace the oxygen you need. You cannot see or smell that happening. You simply become drowsy, and then unconscious.

// if something goes wrong

Leaving is the fix.

Never try to repair, cap or contain a leak while it is leaking. Get out first, then act.

  1. Get everyone out of the space and away from the gas.
  2. Do not switch anything on or off. Do not strike a flame.
  3. Ventilate, but only if you can do it without passing through the leak.
  4. Tell a named adult supervisor immediately.
  5. Anyone who feels faint, dizzy or short of breath must get to fresh air and be checked by a medical professional, even if they seem fine.
// what comes out

The digestate is not just dirt.

Digestate is living biological material. It is a genuinely useful fertiliser, and it is also a hygiene risk.

Handling

Wash, cover, contain

Wear gloves, cover any cuts, and wash your hands properly afterwards. Never eat or drink while handling it.

Disposal

Never into a waterway

Agree where it goes with your school before you build, not after.

// for chapters

What must exist before a build starts.

  1. A named adult supervisor who has read this page.
  2. A written risk assessment for the site you are using.
  3. A first-aid kit within reach.
  4. Written permission from the school, and consent for everyone under 18.
  5. A written decision on where the digestate goes.
A chapter that cannot meet these conditions does not build. There is no version of FRSH where speed matters more than this.
// the limits of this page

Educational material — not engineering advice.

FRSH is a student-led non-profit, not a licensed engineering or safety consultancy. This page is shared for education. Your school's rules, your local regulations and your own judgement come first. If you are not certain a build is safe, do not build it — ask someone qualified.

Start your application → See chapters & the FRSH Score