This is a question that correctional systems across the country have been forced to answer in courtrooms, and the record is not good.
For an inmate placed on active suicide watch, the cell is stripped of almost everything by design. No bedding beyond a suicide-resistant smock and a thin mat, no clothing with strings or drawstrings, no sheets, no shoelaces, nothing that could be fashioned into a ligature. In many facilities the cell has a solid door with a small observation window rather than bars, and a camera mounted in the corner feeds to a monitoring station. The toilet and sink are recessed into the wall with no exposed hardware. Meals come through a slot. The lights stay on around the clock. It is one of the most psychologically severe environments a human being can be placed in, and the cruel irony is that the conditions designed to prevent self-harm are themselves documented to accelerate the mental deterioration that makes someone suicidal in the first place.
For an inmate in isolation for mental health reasons who is not on active suicide watch, the cell conditions are somewhat less restrictive. Basic bedding, a jumpsuit, and limited personal property may be permitted. The camera monitoring may still be present but the level of direct observation is reduced. That gap between suicide watch protocol and standard isolation monitoring is where the system has repeatedly failed.
In both cases the critical safeguard is supposed to be the SHU officer conducting regular welfare checks. Those checks are required at intervals of every 15 to 30 minutes depending on the facility and the inmate's classification. The officer is supposed to make visual confirmation that the inmate is alive and not in distress, log the check, and move on to the next cell. Done properly and consistently, that protocol significantly reduces the window in which a crisis can go undetected.
Done poorly, which the documented record shows happens far too often, the checks become cursory, infrequent, or falsified entirely. Staffing shortages, fatigue, indifference, and a culture of minimal accountability in isolation units have all contributed to deaths that a proper check schedule would have prevented. Several high-profile cases have involved post-incident reviews showing that logged checks never actually occurred.
If you have a loved one in isolation and are concerned about their safety and the adequacy of monitoring, put your concerns in writing to the facility's mental health unit and the warden's office immediately. That paper trail matters. An attorney who handles prisoner civil rights cases is worth consulting if you believe the standard of care is falling below what the Constitution requires.