How Many Air Purifiers a Hospital Ward Actually Needs

Key takeaways

• A ward, nurse station and isolation bay each need independent sizing rather than one shared figure.
• Required CADR equals floor area in square metres multiplied by ceiling height in metres multiplied by target ACH.
• Clinical areas generally target five or more air changes an hour, with isolation-designated spaces set higher still.
• One larger unit can sometimes cover a big open bay more efficiently than several small ones scattered around it.
• A proper survey beats estimating across a whole ward layout with many different room shapes and uses.

Why a Ward, Nurse Station and Isolation Bay Are Sized Separately

It's tempting to treat a hospital ward as one large area and apply a single blanket figure to the whole floor plan. In practice, a ward is a collection of distinct spaces, an open multi-bed bay, a separate nurse station, storage rooms and often an isolation bay, each with its own floor area, ceiling height and use.

A nurse station, for instance, is usually smaller and has different occupancy patterns than the main bed area it serves. An isolation bay carries its own separate risk profile again. Sizing all of them to one number, whether taken from the largest room or averaged across the floor, usually leaves at least one of these spaces under or over covered.

Breaking the ward into its component rooms first is what makes the rest of the sizing exercise accurate. Skipping this step and working from one overall square footage figure is the single most common reason a ward ends up with mismatched coverage.

Applying the CADR Formula to Each Area

Required clean-air delivery rate, CADR, in cubic metres per hour, is calculated as floor area in square metres multiplied by ceiling height in metres multiplied by your target air changes per hour. Apply this formula separately to the main bed bay, the nurse station and the isolation bay, using each room's own measurements rather than the ward's total footprint.

A large open bay with several beds will typically need considerably more coverage than a compact nurse station, which is part of why one figure for the whole ward rarely works. For a bay of significant size, this often points toward the coverage of a heavier-duty unit like the Pro 800S rather than a single small unit stretched beyond its intended coverage. Record each room's measurements as you go, since the same figures will be useful again when servicing schedules are planned later.

Recommended ACH for Clinical Versus Common Areas

The general baseline recommended for a clinical space is five or more air changes an hour. Isolation-designated areas are typically set higher again, reflecting the heightened concern around airborne transmission in those specific bays, while a general corridor or common area may sit closer to the baseline.

Applying the higher target only where it's actually needed, rather than across the entire ward, keeps the specification proportionate rather than over-engineered everywhere. It also means your budget and equipment count reflect where the genuine risk concentration is.

Confirm the specific target for each room type against the current guidance for that area rather than assuming one figure covers every space in a hospital. This is also where a facilities team should document its reasoning, so the specification can be explained consistently if a reviewer or auditor asks about it later.

When One Larger Unit Beats Several Smaller Ones

For a large open bay, a single unit with higher coverage, such as the Pro 800S's 56 to 96 square metre range, can be more practical than several smaller units scattered around the room. Fewer units means fewer filters to change, fewer points of potential failure, and simpler servicing logistics.

Smaller, separate rooms like a nurse station or a compact isolation bay are usually better served by units matched to their own smaller footprint, such as the Classic 400S or Fillo Plus depending on the exact area.

The decision comes down to room shape and size, not a fixed rule that bigger rooms always need multiple units or that one unit always suffices. A long, narrow bay may still need more than one unit even at a modest floor area, simply because airflow doesn't reach evenly across an elongated shape.

Getting a Survey Instead of Estimating for a Whole Ward

A hospital ward's mix of room shapes, ceiling heights and existing aircon infrastructure makes a paper estimate a rough starting point at best. Real measurements per room produce a far more reliable specification than working from typical figures.

A free room-by-room Air Report can cover this across an entire ward in one exercise, giving facilities management an accurate per-room breakdown rather than a single averaged number. Our Air Purifier Size Calculator is a useful starting point for a rough figure before that survey happens.

Treat any quick calculation as a planning tool, and confirm the final specification against actual measured rooms. A ward-wide survey also gives facilities management one consolidated document to reference instead of separate notes for each room.

Next step

For an accurate, room-by-room breakdown across your ward rather than a single estimated figure, use the Air Purifier Size Calculator as a starting point and follow up with a full survey.

Frequently asked

Should a nurse station be sized separately from the main ward area?

Yes. A nurse station typically has a different floor area, occupancy pattern and use from the main bed bay it serves, so applying the ward's overall figure to it usually gets the sizing wrong. Measure and size it as its own room using the standard CADR formula.

What ACH is appropriate for an isolation bay versus a general ward?

A general clinical area targets five or more air changes an hour, while an isolation-designated bay is typically set higher given the heightened concern around airborne transmission in that specific space. Confirm the exact target for your isolation bay against current guidance for that room type.

When does one larger unit make more sense than several small ones?

A single large open bay is often better served by one higher-coverage unit than several smaller ones spread around the room, since it means fewer filters to manage and simpler servicing. Smaller, separate rooms like a nurse station are usually better matched to a unit sized for their own smaller footprint instead.