Ventilation and air quality in silent pods: what you need to know
The acoustics get all the attention with silent pods, but there is a second factor that decides just as much whether people are happy to sit in one: the air quality. A well insulated pod is airtight by definition - and with that a potential CO₂ trap. Within 8-12 minutes the CO₂ concentration in a 1-person pod can rise from 600 ppm (fresh outdoor air) to 1.400 ppm or more, and at that level your cognitive performance drops measurably.
In this article we explain what good pod ventilation involves: what air flow you need, how you keep CO₂ levels stable, which fan noise levels are acceptable and what the relevant filter classes are for health and pollen allergy. We close with test tips you can use to judge a pod 'on air quality'.
In this article
CO₂ and concentration: the measurable effect
Research from the Lawrence Berkeley National Laboratory (Satish et al., 2012), confirmed by TNO, shows that decision-making ability already drops from 1.000 ppm CO₂, and collapses by 50% at values above 1.400 ppm. A Belgian study by KU Leuven found that pupils in classrooms with 1.500 ppm scored on average 12% worse on concentration tests than in classrooms with 800 ppm.
The Dutch occupational health guideline recommends that CO₂ in workrooms stays below 1.200 ppm, with a target value of 800 ppm. In a hermetically closed silent pod without active ventilation, one person hits 1.200 ppm within 10 minutes; with two people in a meeting pod that happens within 6 minutes. So a pod without serious ventilation is not a pod you can work 'productively' in.
| CO₂ level | Working environment | Effect |
|---|---|---|
| 400-600 ppm | Fresh outdoor air | Optimal concentration |
| 700-1.000 ppm | Well ventilated office | No noticeable effect |
| 1.000-1.400 ppm | Poorly ventilated | Decision-making down 5-15% |
| 1.400-2.000 ppm | Stuffy | Headache, drowsiness |
| > 2.000 ppm | Unhealthy | Immediately noticeable cognitive decline |
What is a good air flow?
For a 1-person pod you need about 30-36 m³ per hour (m³/h) of fresh air supply to keep CO₂ stable below 800 ppm. For a 4-person meeting pod that has to rise to 90-120 m³/h. Cheap pods often work with 15-20 m³/h - on paper that looks like enough, but in practice it means your head feels heavy after 20 minutes.
A good pod uses a combined system of mechanical supply and passive extraction, with a sensor-driven booster that scales the ventilation up automatically as soon as CO₂ goes above 800 ppm. At ZMN this is standard in all our pods above the basic entry model - in the basic models we work with a continuous fixed flow that stays below 1.000 ppm even at full occupancy.
Silent ventilation: how do they do that?
The biggest complaint about cheap silent pods is paradoxical: 'it is quiet against noise from outside, but the fan itself is audible'. That comes from the use of standard PC or bathroom fans, which already make 38-50 dB(A) at 1 metre - audible in every call test. A good pod uses an EC fan with a large diameter and low revolutions, which stays below 32 dB(A) at 1 metre - practically inaudible.
On top of that, sound reduction works in the air duct itself: a labyrinth of acoustically absorbent walls makes sure noise from outside cannot get in through the air opening, and that fan noise does not radiate into the pod. This typically costs € 200-450 per pod extra in production costs - which is why budget pods often choose to leave it out.
Filtering and air quality
Besides CO₂, particulates (PM2.5, PM10), pollen and VOCs (volatile substances from furniture, cleaning products, printed matter) play a role. A serious silent pod has at least an F7 filter (to EN 779) or ISO ePM1 50% (to ISO 16890) on the air inlet. With that you filter 70-85% of the particulates and all relevant pollen out of the incoming air.
For allergy-sensitive staff or pods in urban settings (busy streets, a motorway) we recommend F9 or ePM1 80% filters. Those also stop ultrafine particulates and most viruses. Filter replacement is annual; with our subscription that is included in the service contract as standard.
- G4 / Coarse - stops coarse dust and hair; not enough for pollen or particulates.
- F7 / ePM1 50% - the office standard; against pollen and average particulates.
- F9 / ePM1 80% - for allergy-sensitive people or urban settings.
- HEPA H13 / ePM1 95% - for clinical rooms; overkill for an office.
Climate control: heat and humidity
A pod is a small space, and people produce heat. One person gives off about 100W of heat, so four people in a meeting pod give off 400W - comparable to a 400W halogen lamp. Without active cooling the temperature rises from 22°C to 28°C in 20 minutes. Not liveable.
Good pods work with a combination of: passive cooling through air flow, a PTC heating element for cold mornings, and in premium meeting pods an active air conditioning module (split unit or monoblock). For 1-person focus pods, passive cooling is enough in 90% of Dutch offices, provided the air flow is up to standard.
Humidity is a second point of attention. Breathing produces moisture; in a closed pod the humidity rises from 45% to 65-70% in the course of an hour. That is not unhealthy in itself, but combined with heat it can be uncomfortable. The ventilation usually handles this by itself - no control is needed, provided the flow is right.
How do you check air quality yourself?
A CO₂ meter of € 80-150 (an Aranet4 or MIIIaO for example) is enough. Put it in the pod, shut yourself in and work at a normal pace for 20 minutes. With a good pod CO₂ stays below 1.000 ppm in this test; with a mediocre pod it rises to 1.300-1.600 ppm; with a bad pod it shoots through to 2.000+.
Do the same test with 2-4 people in a meeting pod. The limits are higher there because of the capacity, but the principle stays the same. We run this test as standard during demos and share the measurement results with customers - ask other suppliers for that explicitly too.
- Bring a CO₂ meter, calibrate it on outdoor air (~420 ppm) before the test.
- Shut yourself in the pod for 20 min and work at a normal pace (typing, talking, video call).
- Note the CO₂ after 5, 10, 15 and 20 minutes - it has to stay below 1.000 ppm.
- Listen to the fan: can you hear it or not?
- Do you feel air flow on your face or neck? (strong = uncomfortable, none = possibly not enough)
Maintenance and service life of the ventilation
Ventilation is the only part of a silent pod that needs regular maintenance. Replace the filters annually, the fan every 5-7 years (a typical EC motor runs 60.000-80.000 operating hours), and an annual check of the seals around the air ducts. At ZMN this is included in the standard service contract of € 18-32 per pod per month - including proactive replacement.
Pods belonging to customers who neglect the maintenance reach only 60% of their original air flow after 3-4 years. That is immediately noticeable in CO₂ levels and user satisfaction. For the price of a service subscription (€ 250-380 per pod per year) that can be solved preventively.
The key points
- CO₂ in pods has to stay below 1.000 ppm - above 1.200 ppm it costs cognitive performance.
- Good air flow: 30-36 m³/h for a 1-person pod, 90-120 m³/h for a 4-person meeting pod.
- The fan has to stay below 32 dB(A) at 1 metre - otherwise it disturbs the calls it is there to make possible.
- Filter class F7/ePM1 50% is the office standard; F9 for allergy-sensitive or urban locations.
- Always test pods yourself with a CO₂ meter: a 20-minute test, CO₂ below 1.000 ppm = pass.
Frequently asked questions
Not with a pod that has good ventilation. A serious pod refreshes the air in 90-120 seconds and keeps CO₂ below 1.000 ppm. Always test with a CO₂ meter before you buy.
An annual filter change and a check of the seals. EC fans last 60.000-80.000 operating hours - roughly 12-15 years in office use. A service subscription is € 18-32 per pod per month.
Not with a good pod - that works below 32 dB(A) at 1 metre, well under whisper level. With budget pods using PC fans (38-50 dB(A)) it is clearly audible.
Ask for F9 filtering or ISO ePM1 80%. That stops all pollen and most particulates. At ZMN that is an upgrade of € 180-280 per pod.
No, all modern pods use electric ventilation. In a power cut you simply open the door - the pod is ventilated again within seconds by natural convection.
Ready for a quieter workfloor?
Request a no-obligation quote or send a photo of your space - we visualise the pod on site.
