Month: March 2026

Next time you are inside a new AI hall, get down on the slab at the end of a rack row, beside the coolant distribution unit, and look for a thin sensing cable clipped to the floor and run in a loose serpentine around the unit’s feet. That is leak detection cable. It alarms on contact with conductive liquid, and there will be spot sensors to go with it, sitting under the quick disconnects and in the drip trays beneath the manifolds.

Now think about a mop bucket.

That is the job you are being invited to bid for, and the first thing to understand is that almost nothing you know about data centre cleaning from ten years ago applies to it. There is no raised floor. At 100kW and above per rack the plenum has no cooling function, so the AI-era default is slab-on-grade with power busway, coolant supply and return headers and cable tray all routed overhead. No tiles to lift, no subfloor to vacuum, no pedestal heads.

I have watched a great many London commercial contractors add a data centre cleaning page to the website, buy an H14 vacuum, and start bidding. The page and the vacuum are the whole of the capability, and the method statements I have seen attached to those bids describe lifting floor tiles in a building that does not have any. This became a marketing category considerably faster than it became a competence.

What gets cleaned in a new AI hall?

Everything is overhead or vertical, and very little of it is floor.

Above you: busway, coolant headers of 150mm diameter or more, fibre and network tray. Those runs collect settled particulate and they sit directly above open rack tops. In front of you: rack faces, containment doors and roofing, CDU enclosures, rear door heat exchanger coil faces, and filter faces on anything still moving air. The slab is the easy part and the smallest part of the hours.

All of it dry or near-dry. Lint-free wipes, no polish, nothing with silicone in it, no product that will off-gas into a room of intake fans. Vacuums filtered at H13 or H14 with ESD-safe hosing, because a standard plastic hose moving dry particulate builds a charge quite happily.

The standard you will be measured against is ISO 14644-1, most often Class 8, borrowed from cleanroom practice. Your work gets graded by a particle counter rather than by a facilities manager running a finger along a surface, and there is no talking your way past a count.

So what happened to the underfloor work?

It went out with the design, and a good deal of the market has not noticed.

If a tender for one of these buildings specifies subfloor plenum cleaning on a frequency, either it has been copied from a legacy colo specification that nobody technical has read, or the hall is a retrofit AI zone in an older building, which is a different job again.

Ask at site visit stage. Slab or raised floor, air or direct-to-chip, what is overhead. Those answers change your labour model completely, because the work has moved from crawling to working at height.

What goes wrong when a generalist crew does it?

This is the section that matters, because the failure mode here is an outage rather than a complaint. In an office a bad clean produces an email. Here it produces an incident number, a root cause investigation with your company named in it, and a liability conversation your public liability cover may not comfortably reach.

Start with the leak detection, because it is the new risk and the one nobody in general cleaning has ever met. That sensing cable and those spot sensors are tuned to catch a few drops from a quick disconnect before a leak spreads along a cable route and appears somewhere unexpected. They cannot distinguish your damp mop from a manifold weep. A tipped wet vac or a spray bottle overshooting a rack door can put the loop into alarm, and depending on how the site has configured its response, that can mean isolation valves closing on a cooling circuit while GPUs are at load.

The mitigation is a defined exclusion distance from every sensing run, spelled out in your method statement, plus liquid volumes controlled at source. Pre-moistened wipes issued by count rather than bottles and cloths. Nobody carries an open container of anything in the hall.

Then the overhead work, which has replaced the underfloor work as the physical risk. Cleaning busway tops and header runs means access equipment inside a cold aisle that may be 1,200mm wide, between two rows of live racks worth more than the building most of your operatives clean by day. A dropped tool onto a busway is an arc flash conversation. Foreign object control earns its paperwork here: tools and consumables counted in, counted out, signed for, and a lost item stops other people’s work until it is found.

Then airflow, which survives from the old world in a new form. Containment doors get propped open for a hose and left. Blanking panels get lifted out by crews who take them for dust covers. Brush seals at cable entries get pushed aside. Every one of those is a bypass path that sends cold air somewhere other than through the equipment, and the temperature rise happens in a spot where nobody is standing.

Then aspirating smoke detection, which samples air continuously through a pipe network and runs orders of magnitude more sensitive than the point detectors in an office ceiling. It exists to catch the first products of overheating cable insulation. A crew disturbing settled particulate along an overhead tray run can push it into alarm with no smoke anywhere in the building. The zone covering your work gets isolated by the site’s own team before you start, with a documented time out and time in. If nobody on your crew knows to ask for that, you should not be in the hall.

And the ordinary things that are extraordinary here.…