Indoor Air Quality (IAQ) in an Office Building — Filters, Ventilation, and Occupant Health

Office building occupants spend eight, ten, and sometimes twelve hours a day inside it — breathing the same air over and over. And yet, indoor air quality (IAQ) is one of the parameters that almost no building owner in Israel measures, until complaints of headaches, fatigue, and poor concentration begin. The problem is that bad air, unlike a water leak or a stuck elevator, is not "visible" — it accumulates quietly. In this article I will explain what really determines the air quality in a building, how to manage it correctly in practice, and why this is one of the maintenance investments with the highest return on occupant health and property value.

What IAQ Actually Is, and Why It Is Not a "Luxury"

Indoor air quality is the measure of how healthy and pleasant the air inside the building is to breathe. It is made up of several factors that work together:

• CO2 concentration — reflects how much fresh air is coming in relative to actual occupancy
• Respirable particles (PM2.5 and PM10) — dust, pollen, soot
• Volatile organic compounds (VOCs) — released from furniture, paint, cleaning agents, and printers
• Relative humidity — too high encourages mold, too low dries out the respiratory tract
• Temperature — directly linked to comfort and concentration

When one of these deviates, the air turns from a "transparent background" into a factor that directly affects the body. In Israel there is a tendency to treat air quality as something of "green building" or luxury — this is a mistake. In an office building where labor is the tenants' largest expense, a small drop in productivity due to stuffy air is worth far more than any imagined saving on filters. This is not a soft issue — it is a distinctly operational and economic one.

Where Bad Air Comes From — The Three Main Sources

1. Lack of Fresh Air (Under-ventilation)

This is the most common problem I have encountered in Israeli buildings. A powerful HVAC system can cool a space excellently and still suffocate it — if it recirculates the same air over and over without bringing in fresh air from outside. The more people in the space and the less fresh air entering, the higher the CO2 level climbs, and with it the sense of heaviness and fatigue. Many building owners deliberately reduce fresh-air intake to "save on cooling energy" — and in doing so directly harm the occupants. A portable CO2 station that measures the reading over a workday will reveal the problem within hours.

2. Poor Filtration

The air that does enter passes through filters. A clogged filter, one that is too cheap, or one that was not replaced on time does not capture particles — and can even become a breeding ground for bacteria and mold that spread back into the space. In a building near a main road I saw a filter whose replacement date had long passed; a particle test showed concentrations several times higher than the reading outside — meaning the filter had become a source of pollution rather than a guard. A filter is the lung of the building; when it is sick, everyone who breathes gets sick with it.

3. Internal Pollution Sources

Aggressive cleaning agents, laser printers, new furniture that off-gasses VOCs, hidden mold behind an untreated water leak, and even an underground parking garage whose air leaks upward — all pollute the air from within. Here the link to ecological cleaning materials is direct: what you clean the building with becomes part of the air you breathe in it. It is recommended to "air out" recently purchased furniture in a separate space before bringing it in, and especially in glass-enclosed meeting rooms where air exchange is limited anyway.

Filters — The Heart of the Matter

If there is one thing that changes air quality more than anything, it is the correct management of the HVAC system's filters. Filters are rated by filtration efficiency — the higher the rating, the smaller the particles they capture. The critical point that building owners miss: a better filter is not always the answer. A filter too dense for a system that was not designed for it will choke the airflow, overload the fan, and cause under-ventilation — exactly the problem we were trying to solve.

• Matching the system: the filtration rating must match the fan capacity and the system design. Upgrading a filter without an airflow check is a common and costly mistake — verify with the HVAC representative before making a change.
• Replacement frequency: filters get dirty according to load — in a busy building, a dusty area, or near a main road, they must be replaced more frequently than the basic recommendation. The date, not the feeling, decides.
• Sealing around the filter: an excellent filter that the air bypasses from the sides is worth nothing. The installation must be completely sealed, including inspecting the frame.
• Full documentation: every replacement is documented — date, filter rating, technician's name. This is proof of maintenance and a basis for planning the next one; in a dispute with a tenant, it is your defense.

Filter replacement is a perfect example of a cheap and simple action that gets postponed until it becomes a health problem. That is exactly why the annual preventive maintenance checklist exists — so that filter replacement is a scheduled task and not "we remembered when the complaints started."

Ventilation and Fresh-Air Supply — Filtration Alone Is Not Enough

Filtration handles air quality; ventilation handles the quantity of fresh air. These two are separate, and confusing them is a source of common problems. A modern HVAC system in an office building should bring in a certain percentage of fresh outside air and exhaust "used" air. When the system is balanced correctly, the CO2 level stays reasonable even in a crowded meeting room.

In practice, in many buildings I have investigated, the fresh-air intake dampers were partially closed — sometimes deliberately by a technician who wanted to "save on cooling," and sometimes broken and not inspected for years. A physical check of the damper mechanisms once a year eliminates a silent source of ventilation problems.

An advanced solution worth knowing is an energy recovery ventilation system (ERV/HRV): it brings in fresh air but "steals" the cold or heat from the outgoing air before it is exhausted — so you get fresh air without wasting cooling energy. This is exactly where air quality and sustainability and ESG in office buildings meet: you can breathe better and consume less, if the system is designed and maintained correctly.

Ventilation control is also where a building management system (BMS) proves its value: CO2 sensors in spaces enable demand-controlled ventilation — the system increases fresh air when the space fills up and lowers it when it empties. This way you get both healthy air and savings, instead of choosing.

Humidity — The Silent Enemy

Humidity is the parameter easiest to neglect and the most dangerous in the long run. Excessively high humidity (above about 60 percent) creates ideal conditions for mold, dust mites, and bacteria — and in the Israeli climate, especially in cities like Tel Aviv, Netanya, and Haifa with high coastal humidity, this is a real danger particularly in server rooms, document archives, and storerooms. Excessively low humidity (below about 30 percent), common when the HVAC system runs at full power in summer, dries out eyes, throat, and airways.

The most severe problem is hidden mold. A small water leak behind a drywall wall that goes untreated turns within weeks into a mold colony that releases spores into the air — without anyone seeing a thing. The classic signs: a musty smell explained away with "we can't locate the source," a recurring cough among employees seated in a particular corner, humidity stains on the ceiling even after the "leak was fixed." Here the circle closes with plumbing and water system maintenance: every leak not sealed quickly is not just moisture damage, but an air-quality time bomb. Opening the drywall and inspecting visually, rather than just "fixing the leak from outside," is the professionalism that saves problems.

How to Measure — You Cannot Manage What You Do Not Measure

The good news is that measuring IAQ has become cheap and accessible. Dedicated sensors measure the key parameters in real time, and allow you to move from "we think the air is fine" to "we know." What is worth monitoring:

• CO2: the best indicator of ventilation quality. Values approaching 1,000 ppm and above in a closed meeting room indicate a lack of fresh air and are directly responsible for the afternoon fatigue.
• Respirable particles (PM2.5 / PM10): reflect filtration efficiency and the penetration of pollution from outside — especially useful in buildings near busy roads.
• Volatile organic compounds (VOCs): rise after renovation, painting, intensive chemical cleaning, or the introduction of new furniture — monitoring allows you to identify when the levels return to normal.
• Relative humidity and temperature: a basis for comfort and mold prevention; an immediate deviation can be detected before the damage accumulates.

Continuous measurement, rather than a "one-off sample by an external consultant," is what turns IAQ from a document in an archive into a living management tool. When the sensors are connected to the BMS, a deviation triggers an alert and an action — not a complaint. It is important to place sensors in both meeting rooms and the open workspace, because the needs are very different between the two environments.

The Link to Regulation and Standards in Israel

It is important to be precise: in Israel there is currently no single general law that obligates every office building owner to measure IAQ and meet a specific numerical value. However, several frameworks touch on the subject directly:

• Work Safety Regulations (Occupational Hygiene and Health): obligate an employer to provide proper working conditions, including adequate ventilation and prevention of exposure to harmful substances in the work environment.
• Israeli Standard (SI) 5281 for green building: addresses indoor environmental quality as a central axis, including requirements for ventilation, filtration, and the use of low-VOC-emission materials.
• The Safety in Public Places Law and business licensing: require proper environmental conditions — extremely poor air can conflict with license requirements.
• Fire authority requirements: the HVAC system is subject to requirements from the Fire Authority regarding smoke evacuation and system function in an emergency.

In other words: even without a direct "IAQ standard," a building owner who provides poor air is exposed to claims from tenants and employees, to harm to licensing in extreme circumstances, and to a decline in property value. The correct view is to see air quality as part of ongoing HVAC maintenance — a subject expanded on in HVAC system maintenance in office buildings — and not as a separate project waited on until someone forces it to be done.

IAQ Management Plan — Five Practical Steps

In the buildings I manage, an IAQ plan is not a separate document — it is part of the ongoing maintenance schedule. Here is what works:

1. Mapping the system: how fresh air enters, where the filters are, what their rating is, and what airflow the system was designed for. Including a physical check of the damper mechanisms and exhaust openings.
2. Filter replacement schedule: frequency based on real load, documented and scheduled — not by feeling and not by complaints.
3. Ventilation balancing: ensure the amount of fresh air is sufficient for actual occupancy, especially in meeting rooms and dense spaces. If there is no documentation of the fresh-air quantity entering — request an airflow measurement from an HVAC technician.
4. Continuous monitoring: CO2, particle, and humidity sensors — preferably connected to the BMS with automatic alerts on deviation.
5. Fast treatment of sources: sealing water leaks within 48 hours, switching to low-VOC cleaning materials, and isolating pollution sources such as a parking garage, kitchenettes, and chemical storage areas.

The difference between a plan that works and good intentions is, as always, the control. Whoever holds the filter replacement schedule, reads the sensor alerts, and acts on them — is the one who truly manages the air in the building.

Why It Pays — Beyond Health

Clean air is not just a medical matter. It is a competitive asset. A building that can present good air quality data attracts quality tenants and keeps them, especially as international companies enter Israel with strict work-environment requirements. In addition:

• Fewer absences and complaints — good air reduces ongoing illness and cuts down tenants' phone calls to the building manager
• Longer HVAC system life — a clean filter = a system that works more easily, less blockage damage and load on motors
• Energy savings — demand-controlled ventilation saves unnecessary cooling, and an ERV/HRV system returns energy to the process
• Property value and income stability — tenants who feel the building "cares for" them renew their leases

This is exactly where air quality meets comprehensive property management: it is not a one-off project but a maintenance routine — filter replacement, ventilation balancing, reading sensors, and treating sources — that runs in the background, without drama. Professional management is what turns clean air from random luck into a planned, documented outcome.

At Domera we integrate air-quality management into ongoing HVAC maintenance — from the filter replacement schedule to CO2 and humidity monitoring — as part of a comprehensive sustainability approach for the property. Get a quote for an air-quality review of your building.