Nicole Friederichs — Air Purifier

Data

While exploring different everyday environmental issues, I became interested in the hidden disadvantages of using conventional fans indoors.

Although fans help circulate air and provide temporary comfort, I discovered that when they operate without any filtration system, they can also redistribute dust particles, allergens, and bacteria already present in the room.

This immediately caught my attention because I noticed the same situation in my own home, especially in my father's office, a small space with very limited natural ventilation, where air tends to remain stagnant for long periods of time. In that environment, using a regular fan only moves the same contaminated air around instead of actually improving its quality.

Once I identified this as a real and familiar problem, I decided to look for objective data and scientific evidence to better understand how indoor air circulation without filtration can negatively affect health and cleanliness. During my research, I found that:

99% of the population breathes air that exceeds the quality limits recommended by the WHO On average, people spend approximately 90% of their time indoors, where concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations. Household air pollution was responsible for an estimated 2.9 million deaths per year in 2021, including over 309 000 deaths of children under the age of 5.

Factors that contribute to a more dangerous indoor environment:

Poor ventilation
dust accumulation
humidity
fine particles
cooking smoke
textiles
cleaning chemicals
pets
nearby traffic
dense urban areas

Principal Air pollutants

Material particulado
(PM2.5 y PM10)

Dióxido de
nitrógeno (NO₂)

Monóxido de
carbono (CO)

Dióxido de
azufre (SO₂)

Ozono
troposférico (O₃)

Compuestos
Orgánicos
Volátiles (COV)

User

Young adults and students/professionals who spend long days in closed rooms, studios or home offices and experience fatigue, heavy air, dust or allergies, are looking for a compact solution that improves their comfort and daily health.

Effects of pollutants:

respiratory system
allergies
asthma
fatigue
headache
eye irritation
mental concentration
sleep quality

After analyzing these findings, I understood that indoor air pollution is not an isolated issue, but a constant condition in many everyday spaces where people study, work, and spend most of their time.

This revealed an opportunity to design a compact solution that could both improve airflow and purify the air for people who spend long hours in enclosed spaces.

Concept

Spiral Development

To make this project I will be using the spiral development method. It consists of a risk-driven approach for projects that delivers work in a series of iterative cycles rather than a fixed linear sequence

Objective

Design and build a modular indoor air purifier capable of adapting to different filtration needs through interchangeable modules. The system must allow for quick, safe, and easy removal and replacement of filters, minimizing direct contact with accumulated contaminants.

Problem

Indoor environments have high concentrations of pollutants such as PM2.5, dust, pollen, smoke, volatile organic compounds (VOCs), odors, carbon dioxide, and microorganisms. Many conventional air purifiers have fixed filters that are difficult to replace and not very adaptable to different scenarios.

Project requirements

The purifier must allow the installation or removal of filtration modules depending on the type of predominant contaminant.
The modules must be interconnectable.
A fan must exhaust clean air from the top or front.
The design must prevent incorrect filter installation.
A sealing system must be in place to prevent air leaks between modules.
The system must draw in contaminated air from one side of the unit.
Air must pass through the filters in a logical order.
At least two operating speeds must be available.
The user should not directly touch the contaminated surface of the filters.
It must include LED indicators or a simple display. (Power on/off status, Air quality, Filter saturation, Fan speed)
It should generate little noise during normal operation.

Proof of Concept Validations

Filtration: Measure the change in the air particles before and after.
Modularity: Absence of air leaks after reinstalling the module.
Intuitive: The filter replacement has to be intuitive.
Fan speed: The fan speed should vary according to the selected power.

Risk analysis

Risk	Impact	Probability	Mitigation
Air leaks between modules	Efficiency reduction	Medium	Use of airtight seals
Low fan power	Insufficient filtration	Medium	Correctly size flow rate and static pressure
Excess noise	Bad user experience	Medium	Experiment with the blades and isolate vibrations
Contact with contaminated filters	Health risk	High	Design closed cartridges
High cost of HEPA filters	Budget increase	High	Design modules compatible with commercial filters
User forgets to change filters	Decreased effectiveness	High	Add visual alerts and timers

Spiral development phases

Filters

Spiral Development

To make this project I will be using the spiral development method. It consists of a risk-driven approach for projects that delivers work in a series of iterative cycles rather than a fixed linear sequence