Negative-Pressure Isolation Room Design for Pakistani Hospitals

The COVID-19 pandemic exposed a gap in many Pakistani hospitals: there were very few rooms that could safely hold a patient with an airborne infection. Tuberculosis, measles, chickenpox, influenza and new respiratory infections all spread through the air, and a single poorly designed “isolation room” can expose nurses, doctors and other patients to serious risk. This guide explains isolation room design for hospitals, with a focus on negative-pressure rooms, and shows how to plan, build and maintain them in Pakistan’s climate and construction conditions.

Whether you are building a new hospital, upgrading an ICU, or converting existing rooms after an inspection, the principles are the same. An isolation room works only when architecture, HVAC, controls and daily operation are designed together. A room with a sign on the door and an exhaust fan in the window is not an isolation room.

🏢 About Hospital Design Hub

Hospital Design Hub is a specialist hospital design and construction company, established in 2000 and focused on healthcare infrastructure: design, construction, consultancy and project management, and the renovation and maintenance of hospital facilities. With more than 50 successfully completed projects, our team has worked on healthcare facilities across Pakistan, including projects such as LDMC, MCH Islamkot, King Edward Medical University / Mayo Hospital, and UOL Hospital Lahore.

Infection control is built into every hospital we design. Our architects and HVAC engineers plan isolation rooms together, so pressure, airflow, sealing and monitoring actually work on site, not just on drawings.

🦠 Types of Isolation Rooms in a Hospital

“Isolation” means different things for different patients. Before designing anything, the hospital must decide which types it needs and how many.

Most secondary hospitals in Pakistan need a small number of AIIRs in the emergency department, the medical ward and the ICU, plus single rooms for contact isolation. Tertiary and oncology centres also need PE rooms. International references such as the US Centers for Disease Control and Prevention (CDC) guidelines and the ASHRAE 170 ventilation standard (ASHRAE) are widely used for design criteria.

🌬️ How a Negative-Pressure Room Works

The idea is simple: air must always flow into the isolation room, never out of it. This is achieved by exhausting more air from the room than is supplied to it. The difference is made up by air leaking in from the corridor or anteroom, under and around the door. Because air flows inward, infectious particles released by the patient are carried to the exhaust rather than out into the corridor.

Several conditions must be met at the same time for this to work:

1. Controlled pressure difference: the room is kept at a stable negative pressure relative to the corridor, commonly a minimum of about 2.5 Pa.
2. High air change rate: 12 or more air changes per hour dilute and remove airborne particles quickly.
3. Directional airflow inside the room: clean supply air enters near the door or staff working area, and exhaust is taken near the head of the bed, so air moves from clean to less clean zones.
4. Safe discharge: exhaust air is ducted separately to the outside, discharged away from air intakes, windows and public areas, with HEPA filtration where the discharge location is not safe.
5. A tight room envelope: without sealing, the room cannot hold pressure and air leaks in unplanned ways.

📐 Isolation Room Design Requirements

🚪 Why the Anteroom Matters

Every time the door of an isolation room opens, the pressure difference collapses briefly and air can move out with the person leaving. An anteroom acts as an airlock: staff enter the anteroom, close the outer door, and only then open the inner door. The anteroom also gives a dedicated place to put on and remove personal protective equipment (PPE), to wash hands, and to store gowns, masks and gloves.

In Pakistani hospitals where space is tight, we often see isolation rooms without anterooms. They can still work, but the risk of leakage is higher and staff discipline becomes even more important. For new hospitals and ICUs, including an anteroom in at least the main AIIRs is strongly recommended.

❄️ HVAC Design for Isolation Rooms in Pakistan’s Climate

Pakistan’s heat and humidity make isolation room HVAC more challenging than in cooler countries. High air change rates bring large amounts of hot outdoor air into the building, which must be cooled and dehumidified. Key design decisions include:

• Dedicated exhaust fans for isolation rooms, on standby power, preferably with duty/standby fans for critical rooms.
• Treated supply air from an air handling unit with proper filtration, rather than relying on split units, which recirculate room air and cannot create a controlled pressure.
• Energy recovery only through systems that do not allow exhaust air to mix with supply air.
• Humidity control to prevent condensation and mould in the monsoon season.
• Balancing dampers and airflow measurement so the system can be commissioned and re-balanced as filters load.
• Location of the exhaust discharge on the roof, away from fresh-air intakes, windows and occupied areas.

Split air conditioners are very common in Pakistani hospitals, and they are acceptable for comfort cooling in some areas. But a split unit alone cannot create a negative-pressure isolation room, because it moves air around inside the room without controlling how much enters or leaves. A split unit can be combined with a dedicated exhaust and a fresh-air supply, but the pressure and air change rate must still be engineered and verified. Learn more on our page on HVAC and climate control systems and in our guide to hospital HVAC and medical gas systems.

⚖️ Permanent AIIR vs Portable Negative-Pressure Units

✅ Pros and Cons of Investing in Negative-Pressure Rooms

🏗️ Construction Details That Make or Break an Isolation Room

We regularly see isolation rooms that were designed correctly but fail on site because of construction details. The most important points are:

• Walls to the true ceiling slab: partitions that stop at the false ceiling allow air to leak over the top. Walls should run to the structural slab, or the ceiling must be fully sealed.
• Sealed penetrations: every cable tray, pipe, conduit and duct passing through the room envelope must be fire-stopped and air-sealed.
• Sealed light fittings and diffusers: use gasketed fittings rather than open fittings that connect to the ceiling void.
• Door gaps: the gap under the door is part of the design; too large and pressure cannot be maintained, too small and the door can be hard to open.
• Hygienic finishes: seamless vinyl flooring coved to the walls, smooth washable wall finishes and cleanable ceilings. See our guide to hygienic materials for OT and ICU.

🔎 Testing, Commissioning and Ongoing Checks

An isolation room must be proven to work before the first patient is admitted, and checked regularly afterwards:

1. Airflow measurement: supply and exhaust volumes measured and air change rate calculated.
2. Pressure verification: differential pressure measured with doors closed; smoke tests at the door gap confirm air flows inward.
3. Alarm testing: pressure monitor alarms tested for loss of pressure and fan failure.
4. Standby power test: exhaust fans confirmed to restart on generator supply.
5. Routine checks: daily visual check of the pressure monitor when occupied, and periodic re-testing and filter replacement as part of planned maintenance.

📊 How Many Isolation Rooms Does a Hospital Need?

There is no single number for every hospital, because it depends on the local burden of TB and other airborne diseases, the services offered, and the hospital’s role in outbreak response. As a planning starting point:

These are indicative planning figures. Your infection control committee and local epidemiology should guide the final number. See also our guides to ICU design standards and emergency room design.

🛠️ Our Isolation Room Solution

For new hospitals and upgrades, Hospital Design Hub provides a complete isolation room package:

• Needs assessment with your infection control team.
• Room and anteroom layout, finishes and door design.
• HVAC design with dedicated exhaust, pressure control and monitoring.
• Construction with sealed envelopes and verified penetrations.
• Testing and commissioning with documented results for inspectors.
• Phased conversion of existing rooms where full new construction is not possible, including a PEB or modular isolation ward for rapid capacity.

Regulators such as the Punjab Healthcare Commission assess infection prevention and control during licensing, and guidance from the World Health Organization on infection prevention in health facilities is a useful reference for hospital policy.

🚑 Where to Place Isolation Rooms in the Hospital

Location is as important as engineering. An isolation room in the wrong place forces infectious patients to travel through crowded corridors, lifts and waiting areas, which defeats the purpose. Good planning places AIIRs where suspected cases first arrive and where the sickest patients are treated:

• Emergency department: at least one AIIR close to the ambulance entrance and triage, so a coughing patient with suspected TB can be isolated immediately rather than waiting in the main hall.
• Medical ward: AIIRs at the end of a wing, near a service lift, so admissions do not pass the whole ward.
• ICU: at least one isolation cubicle with full critical-care services, visible from the nurse station through a glazed wall or door.
• Paediatric and maternity areas: isolation options for measles, chickenpox and infectious mothers or newborns.
• Dedicated route: where possible, a planned route from the ER to the isolation ward and to radiology that avoids public waiting areas.

🧤 Designing for Staff Safety and PPE Workflow

Most infections acquired by healthcare workers happen during routine tasks: entering and leaving rooms, removing PPE, and handling waste. The building should make safe behaviour easy:

• Clear donning and doffing zones: put on PPE in the anteroom or at the entrance, and remove it in a defined area close to the exit, with a mirror and step-by-step signage.
• Hand hygiene at every transition: hand-wash basins and alcohol rub dispensers at the anteroom, inside the room and outside the exit.
• Clinical waste disposal: foot-operated bins for used PPE inside the anteroom, with a safe collection route.
• Visibility: vision panels and, for ICU rooms, glazed walls so staff can observe patients without entering unnecessarily.
• Communication: nurse call and intercom so staff inside can request supplies without opening doors repeatedly.

These details cost very little when included at the design stage, yet they have a major effect on staff protection and on how well the isolation room performs day to day.

❓ Frequently Asked Questions

What is a negative-pressure isolation room?

It is a single-patient room where more air is exhausted than supplied, so air always flows into the room from the corridor. This prevents airborne infectious particles from escaping to other areas.

How many air changes per hour does an isolation room need?

Airborne infection isolation rooms are commonly designed for 12 or more air changes per hour, with all exhaust air discharged safely to the outside.

What pressure difference is required for an isolation room?

A common design target is a negative pressure of at least about 2.5 pascals relative to the corridor, continuously monitored with an alarm.

Does an isolation room need an anteroom?

An anteroom is strongly recommended. It acts as an airlock, provides space for PPE and hand washing, and reduces air leakage when doors open.

Can a split AC create a negative-pressure room?

No. A split unit only recirculates room air. Negative pressure requires a dedicated exhaust system and controlled supply air, although a split unit can be used alongside them for cooling.

What is the difference between negative and positive pressure rooms?

Negative-pressure rooms keep infectious air in to protect others. Positive-pressure protective environment rooms keep outside air out to protect vulnerable patients such as transplant recipients.

How often should isolation rooms be tested?

They should be tested at commissioning, monitored daily when occupied, and re-tested periodically as part of planned HVAC maintenance and after any system changes.

Can existing hospital rooms be converted into isolation rooms?

Yes, if space, structure and ductwork routes allow. Conversion usually involves sealing the room, adding dedicated exhaust, a pressure monitor and ideally an anteroom.