Sampling-point planning under the WELL Building Standard, a certification mark of the International WELL Building Institute, is governed by defined quantity and placement rules rather than an unrestricted choice by the tester. For air verification, the scheme's performance verification guidebook uses a Test Quantity table in which the required number of sampling points is driven by exactly two variables: the project's total area band and its number of floors. This page explains that logic, the required sampling height, the type of spaces represented and the separation principles that make a rule-based plan more defensible than personal discretion.
A sampling plan determines how much of a project is represented by the on-site evidence. If quantity were left entirely to individual preference, similar buildings could be tested very differently, making results harder to compare and defend. The guidebook instead establishes a repeatable method for determining the number of air sampling points.
The Test Quantity table does not ask the testing agent to select a number from a general impression of complexity, convenience or perceived risk. The quantity follows from the two stated project variables. That gives developers, consultants, performance testing providers and reviewers a common basis for understanding why a particular number was used.
The table sets how many points are required, while the placement rules determine whether those points properly represent the project. Quantity and location must therefore be considered together, but neither should be replaced by an unsupported preference.
The first variable is whether the project's total area is below 50,000 square feet or at or above 50,000 square feet, as set out in the scheme's performance verification guidebook. The threshold is approximately 4,600 square metres. This creates two area bands for applying the Test Quantity logic.
The relevant figure is the total area within the applicable certification boundary, not merely the area of a convenient floor or the portion available on the testing day. Establishing the correct boundary is therefore essential before the number of points is selected.
The distinction between below the threshold and at or above it must be applied precisely. A project at the stated threshold belongs in the larger area band. No third area category should be invented for very small, very large or mixed-use projects.
The second and only other variable is the number of floors in the project. Floor count is used because a taller or more vertically distributed project requires a different quantity of sampling points from a single-floor project within the same area band.
The guidebook's range begins at 2 air sampling points for a one-floor project in the smaller area band. At the other end, it reaches 10 air sampling points for a project of more than 20 floors in the larger area band. These figures come from the Test Quantity table in the scheme's performance verification guidebook.
Intermediate combinations are determined from that table, but reproducing its full sequence is neither necessary nor appropriate for an independent explanatory page. The important principle is that quantity is derived from floor count and area band together, not from an informal judgement about how many points appear sufficient.
The air test quantity is driven by exactly two variables: total area band and number of floors. Occupancy density, room count, perceived air quality, tenant preference, available time and the tester's personal risk assessment do not replace those inputs when determining the table quantity.
Professional judgement remains necessary when choosing representative locations within the required quantity and applying the separation rules. It operates inside the guidebook framework rather than deciding whether that framework should apply.
A defensible plan can state the project area band, the floor count and the resulting quantity selected from the guidebook. A plan based only on statements such as "sufficient points were chosen" or "locations were selected at the tester's discretion" is weaker because it does not demonstrate application of the rule.
Air sampling points must be positioned between 1.1 and 1.7 metres above the finished floor, equivalent to 3.6 to 5.6 feet, according to the scheme's performance verification guidebook. The range is specific and should be used in planning, field records and quality checks.
The commonly repeated range of 1.0 to 1.8 metres is incorrect for this requirement and should not appear in the sampling plan. Expanding the range for convenience changes the stated guidebook condition and can place the inlet outside the permitted band.
The reference is to height above the finished floor. Temporary platforms, furniture surfaces or measurements taken from an unfinished construction level can create ambiguity unless the final floor datum is clear.
Sampling points must represent occupiable areas and should preferably be placed in regularly occupied areas. This directs the plan towards spaces reflecting the project's intended human use rather than locations selected solely because they are open, convenient or close to access routes.
An occupiable-area requirement does not mean that every room receives a point. The Test Quantity table sets the total number, and those points must then be distributed so that the chosen locations provide an appropriate representation of the project.
Regularly occupied areas are preferred because they generally provide a stronger connection to ordinary building use. Plant rooms, circulation routes or other convenient spaces should not displace representative occupiable locations merely because they simplify access.
Sampling points must be appropriately separated from walls, openings, HVAC outlets and occupants. These separation requirements reduce the chance that a point is dominated by a highly local condition that does not represent the selected occupiable area.
The principle should be applied during the site walk-through, not only after equipment has been placed. A location that appears central on a drawing may be unsuitable if an outlet, opening, wall or occupied workstation creates an immediate local influence.
A replacement point must still represent an occupiable area, preferably a regularly occupied one, and remain part of the planned distribution. Field records should make the location understandable and connect it clearly to the relevant area.
A rule-based plan can be reconstructed by another competent party. The project area is assigned to the correct band, the floors are counted, the guidebook table supplies the quantity, and the placement rules guide each location. This creates a transparent chain from project facts to field activity.
A discretion-led plan is harder to defend because the number and locations may depend on undocumented preferences. Even an experienced tester can select reasonable-looking points without demonstrating that the scheme's quantity rule was followed. Experience supports application of the rule; it does not replace it.
The defined approach also improves coordination. Project teams can arrange access and readiness for the required locations before the visit rather than discovering on site that too few areas are available.
Timing remains separate. The guidebook does not impose a universal rule that every test occurs during normal occupied hours; timing is set by parameter and project type, with defined exceptions. Water, light, sound and thermal-comfort verification are addressed on their respective pages rather than re-explained here.
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Exactly two variables determine the Test Quantity table selection: whether total project area is below or at or above 50,000 square feet, approximately 4,600 square metres, and the number of floors. The quantity should not be selected from personal preference.
The guidebook range runs from 2 sampling points for a one-floor project in the smaller area band to 10 sampling points for a project of more than 20 floors in the larger area band. Intermediate quantities are obtained from the guidebook table rather than reproduced here.
Air sampling points must be between 1.1 and 1.7 metres above the finished floor, equivalent to 3.6 to 5.6 feet. The wider range of 1.0 to 1.8 metres is not the applicable requirement.
No. Points must represent occupiable areas, preferably regularly occupied areas, and must be appropriately separated from walls, openings, HVAC outlets and occupants. Convenience alone is not a sufficient criterion.
Yes, but it operates within the guidebook rules. Area band and floor count determine quantity, while professional judgement helps select representative compliant locations without changing the prescribed logic.
There is no universal rule requiring every parameter to be tested during normal occupied hours. Timing depends on the parameter and project type, with defined exceptions, and should not be confused with the separate rules determining air sampling quantity and location.
This site is an independent information resource. It is not affiliated with, endorsed by, accredited by or authorised by the International WELL Building Institute pbc, which owns the WELL certification mark, and it is not a certification body, an assessor, a performance testing provider or a scheme partner. Nothing on this page can certify, assess or award anything under the scheme, and nothing here is a substitute for the scheme's own published documentation. Requirements are summarised factually rather than reproduced; where a numeric threshold is stated it is drawn from documentation the scheme's owner publishes openly, and the specific figure is cited rather than the table it sits in. Certification under the scheme is voluntary and is not required by any authority in the United Arab Emirates.