He blew a blood-alcohol reading of .239 and while it would seem the man had too much booze, officers and a nurse can't be sure it wasn't a more sinister substance that has rendered him unconscious.

It's nearly midnight on a blustery Saturday when the man is brought into the sterile collection of cells that make up the ACT Watch House, beneath City Police Station, in the heart of Civic.

The holding facility serves as a temporary home for alleged crooks who are arrested and detained until they can appear in court, as well as troublesome drunks who are often released after they've spent the night in one of the sober-up cells.

Beat officers who brought the unresponsive man in tell the watch house's officer in charge Sergeant Bill Evans they found him lying in a gutter with no shoes or pants on.

"Serg, his pupils are the size of saucers," says one officer.

"Have you had any drugs at all mate?" Sergeant Evans asks.

"Mate, what've you had? You're not in trouble, we just need to know so we can look after you."

The man is placed in a padded, high-risk cell as police officers closely monitor his condition. When he deteriorates, the watch house nurse phones paramedics and he's taken to hospital.

"Ice they're bouncing off the walls, but this is the result of alcohol and whatever else he's taken," Sergeant Evans says.

"He'll probably do it all again next weekend."

It doesn't faze Sergeant Evans, a veteran of the territory's watch house, who says his team's priority is to keep the night-time detainees safe.

"You can tell by the weather, it's going to be a busy night," he says.

"It ebbs and flows, sometimes we'll get 20 people in here, sometimes we'll get three. And it changes, some nights it'll all be drugs, other nights it'll be all drunks."

Police snap into action every time the phone rings and use a whiteboard, CCTV cameras and two-way intercoms to keep tabs on detainees from a central hub.

As an alert sounds and video footage shows a police van pulling into the watch house, officers smack liquid disinfectant into their hands and snap on rubber gloves.

Their first task, Sergeant Evans says, is to distance themselves from the beat cops who brought them into custody and de-escalate any tense situations.

"Sometimes it works, sometimes it doesn't.

"We don't want to hold people here, we want to get them out."

None of the men and women want to be there either, and many try to shrug off the police who lead them inside.

Detainees are brought to the charge counter and searched before Sergeant Evans runs through a list of standard custody questions and they're led to their cell.

It's not unusual for officers to confiscate hidden blades, knives, drugs and knuckledusters.

Sergeant Evans said the vast majority of people who passed through were affected by alcohol and drugs including cannabis, heroin and, increasingly, ice.

"The stimulants are the really bad ones because they'll thump on the cells and throw things, and that can last for six or seven hours.

"With ice people wake up and say, 'I don't remember what I did last night'.

"They'll bite, they'll cut themselves and throw their blood on you."

Officers say detainees have spat at them, urinated on their hands and hurled faeces.

Sergeant Evans estimates about 70 per cent of the detainees also suffer from mental health problems such as depression, anxiety and schizophrenia, often as a result of their drug habits.

Cells for high-risk visitors have padded walls that are torn and covered with explicit graffiti. Drawers filled with spit hoods, gas masks and soft restraints signal the challenges regularly posed by violent detainees.

A few dry cells are without sinks and water so alleged attackers and murderers can't wash blood from their hands and clothes.

At the other end of the spectrum are the non-violent drunks.

About 1am an intoxicated man, who giggles as police search him, admits he's had eight beers and seven bourbons already that night as Sergeant Evans reads out his list of questions.

"Nup. Nup. Nup," the man replies.

"Have you ever been held in custody?" Sergeant Evans asks.

"Yep."

"Had to get get you one one, didn't I?"

By 3am a steady stream of intoxicated men has kept police on their toes. A mother has arrived to bail out her teenage son; a man in custody begins to sing on his bed; officers rush into a cell when a detainee threatens self-harm.

As they walk back to the main hub the phone rings, and the closest officer picks it up.

"We've got another one coming from Belconnen, he's aggressive," she declares.

The police are on their feet again and snap, go the rubber gloves.