Making DIY High-Performance Air Purifier for Delhi: Build Guide

For rapid building and deployment in extreme AQI conditions (999+ PM2.5), I aim to provide you a tested, cost-effective air purifier design structure achievable in 1–2 weeks if built with consistency, using repurposed materials and minimal investment. I will be sharing my condition and output results with this purifier unit.

TL;DR

• Why this matters: You have materials already with you (like fan, wooden or plastic box)

  • Ground-level PM2.5 levels: 800-900+ µg/m³ (vs. government-reported 300-400 AQI)
  • Winter season duration: October-February (4-5 months of hazardous air)
  • Commercial purifier gap: ₹10,000-61,000 for 150-350 CFM
  • Your DIY solution: ₹4,000-5,000 for 550-900 CFM = 5-6x better performance/₹

• What you'll build: 550-700 CFM effective purifier (5-6x better than ₹16,000 commercial units)️⃣

• Cost & Time: ₹4,000-5,000 upfront, ~₹216/month to run, 1-2 weeks to build

• Expected outcome: 12-20 air changes/hour for a room size of ~99 sq ft., noticeable 80-90% PM2.5 reduction in 15-20 minutes️⃣

️⃣ - Check important points of consideration and when/NOT to build section for more info about `(️⃣)`

Important Considerations: Making the Right Decision

🧧 Let me be clear: I am not doing any kind of competition with commercial brands and NOT hyping up my solution in any way until I get data backed outcomes. I'm confident on my calculations and sharing this as a solution for community based on the practical performance response of my unit.

Build Tips: 1-2 weeks to build only if built continuously, prioritize function over aesthetics, avoid using paints that'll increase VOCs in your room making you filter ineffective in initial days. If you think you got late this season, don't loose hope, air is still and will stay unhealthy for breathing for you for your family, the right time is now, build so strong that it last 5+ years.

When to BUILD This System

• You have an industrial exhaust fan (or similar 1500-2000+ CFM fan, check the mentioned ratings)
• You live in high-pollution zone (Delhi, NCR, Lucknow, Agra, etc.)
• Commercial purifiers are unaffordable or insufficient CFM for your room or you simply don't want to invest in a commercial air purifier yet
• You can dedicate 2-4 weeks to building
• You understand this is EMERGENCY response

When NOT to Build (Redirect to Alternatives)

• Genuine HEPA unavailable: DO NOT consider buying MERV 13-15 filters (not HEPA-like, HEPA-style) ONLY H13 true HEPA. Or you'll compromise with your health by selecting wrong type. I'd recommend Coway Original Anti-Virus Green H13 True HEPA Filter

• A fan with weak specifications: Kitchen exhaust fans designed for 10+ hour continuous use (2-4 hrs/day). Verify specs, don't go for 6" exhaust fans by watching a couple of reels they're just there for views, eventually the small exhaust motor will get under high load when sucking air through dense HEPA filter and can surely cause overheating of motor, reducing efficiency of motor in long term.

  • ⚠️ Potential risk of burning it!

• Budget constraints: If you are unwilling to invest ₹4,000-5,000, use passive methods (ventilation, N95 masks) instead. Until you get a new air purifier unit.

• Commercial purifier already owned: If you have 150+ CFM, optimize it instead (add passive carbon, properly servicing it). Don't duplicate unless covering 2+ rooms.

• No space/structural capability: CR box requires 20×20×20 inches cube space. Wooden frame needs a professional carpenter cause you'd not want to ruin your existing or new timber. My current version is bulky and will take space.

What to Expect (Realistic Outcomes)

• Air clearing speed: Breathing feels easier and lighter within 20-30 minutes (again I am reminding with a 13" industrial fan), overnight sleep comfort (10+ hrs continuously running)

• Filter lifespan: HEPA lasts 6 months at Delhi 999+ AQI (10 hrs/day operation)

• Maintenance: Weekly prefilter rinse, monthly fan intake cleaning

• Electricity cost: ₹216/month (sustainable, not a burden)

• Noise level: 56 dB(A) - acceptable background hum, not intrusive. Also works as a noise machine to overcome outside disturbances

Bill of Materials (Complete, Unified)

Summary Table (Quick Reference for Shoppers)

Category 1: PRIMARY FAN

• Component: Crompton 90W exhaust fan
• Specifications: 13-inch blade, 1400 RPM
• Why I chose: Industrial-grade rated CFM 2000, reliable power in Delhi conditions, 90W slightly higher power draw than company's air purifier units, but I chose power and fast cleaning and air changes
• Cost: ₹0 (I already own)
• Status: VERIFIED

Category 2: HEPA FILTRATION (CRITICAL)

• Component: Coway Airmega 150 (AP-1019C) filter
• Specifications: H13 true HEPA, 11"×14.5"×1", 99.97% @ 0.3µm, expect 60-80% drop in CFM
• Why Coway: Genuine media (not MERV 13), affordable (₹3,499), compact, proven in India
• I bought without activated carbon, only H13 filter
• ⚠️ WARNING: Do NOT buy unbranded "HEPA-equivalent", buy true H13 from the Coway official

Category 3: PREFILTERS (PROTECTION LAYER)

• Coarse Mesh: 0.5" cell size
• Fine Mesh: 1mm cell size, steel
• Why two layers: Coarse catches debris >100µm; fine catches dust and grime build-up 5-100µm. Protects HEPA, extends lifespan of filter
• Indefinite reusability: Rinse with water, air dry

Category 4: HOUSING & SEALING

• Cube: 20×20×20" CR box (cardboard) or wood frame
• Foam gasket: 25-50mm thick, adhesive-backed, 5m roll (₹150)
• Rubber gasket: 3-5mm for fan mounting (₹75)
• Duct tape: Backup sealing (₹40)
• Cable grommet: Foam seal around power cable (₹50)
• Total sealing cost: ₹315

Category 5: ELECTRICAL & SAFETY

• Go to your electrical shop tell them the ratings of your fan and ask for a compatible/safe copper cable, plug, regulator for speed control (OPTIONAL, for noise tuning and running on low speed after rapid cleaning)
• Don't do cost cutting on electrical items, keep a room slightly higher than rated specs

Category 7: OPTIONAL - PASSIVE VOC CONTROL

• Component: Raw bituminous coal (NOT activated)
• Specifications: 3kg, 4-8mm granules, open mesh tray
• Cost: ₹1,000-1,500
• Why passive (not inline): Inline carbon reduces CFM by 70-85%; Delhi is 99% PM2.5 (not VOC-heavy)
• Effectiveness: 60-80% VOC removal weeks 1-4, declining by week 8
• Regeneration: Sun-bake 4-6 hours every 4-6 weeks (extends life to 5-6 months)
• ⚠️ DISCLAIMER: Passive coal is secondary; primary threat is PM2.5 (HEPA handles this)

Design & Visual Architecture

3D Assembly Diagram / Blender Render Description

What the diagram should show:

TOP VIEW (looking down):
┌─────────────────────┐
│   FAN (exhaust)     │  ← Crompton 90W mounted perpendicular
│   [circular duct]   │
└─────┬───────────────┘
      │ 
      │ (perpendicular configuration)
┌─────▼───────────────┐
│  HEPA FILTER        │  ← Horizontal orientation, center of cube
│  [pleated media]    │
└─────┬───────────────┘
      │ 2-3mm gap
┌─────▼───────────────┐
│ FINE MESH (0.4-1mm) │  ← Interior layer
└─────┬───────────────┘
      │ 2-3mm gap
      │
┌─────▼───────────────┐
│ COARSE MESH (3.4mm) │  ← Exterior intake face
└─────────────────────┘

    POLLUTED AIR IN

Structural Description

• Sealed cube (cardboard or wood)
• Intake on left face (meshes stacked perpendicular)
• Fan exhaust on top face (perpendicular to intake)
• No other openings
• Interior pressure slightly positive when fan running (ensures air follows correct path)

Key design principle: Perpendicular filter stack + vertical air gap = Low bypass risk + Reduced pressure drop

Assembly Process

Step 1: Planning & Sourcing

• Order goods from Amazon (lead time 3-7 days start)
• Research aluminum mesh local sources
• Collect all materials locally
• Prepare workspace (clean, dust-free corner of room)
• Gather tools

Step 2: Box Construction & Filter Installation

Build Cube Housing

• Assemble your box according to fan mount (if cardboard)
• OR prepare wood frame with the help of a professional carpenter
• Create intake opening (left face)
• Create exhaust opening (right/top face)
• Seal 5 remaining faces completely (no other openings)

Prepare, Cut and Install Coarse & Fine Meshes

• Mount coarse 3.4mm mesh on exterior of intake face
• Mount fine 0.4-1mm mesh inside cube behind coarse mesh
• Fit check

Install Fan

• Mount fan on perpendicular face
• Can use rubber gasket for vibration isolation
• Seal all mounting points with foam tape
• Test sealing before proceeding

Install HEPA Filter Last

Complete Sealing & Test

• Inspect all seams for visible gaps
• Apply additional foam tape to any gaps >2mm
• Incense smoke test without HEPA filter (see testing section for details)
• Light passing/leaking test for edges and corners
• Mark any visible leaks
• Reseal marked areas

Step 3: Electrical & Deployment

1. Verify fan motor specs (230V AC, 0.43A, 90W)
2. Install cable (1.0mm² copper minimum)
3. Seal hole around cable with gasket
4. Test with electrical tester, around the chassis of metal fan and any metal components like nails to ensure there's is no current leakage

First Operation & Baseline

1. Fan speed progression: LOW → MEDIUM → HIGH (verify smooth operation)
2. Run 30 minutes at each speed
3. Check for unusual noise/vibration, abnormal heat on surfaces of motor, switches main panel of your home (Don't poke your fingers in the socket openings)
4. Incense smoke test again in fan running condition without HEPA
5. Document baseline room conditions

Step 4: Continuous Operation & Monitoring

• Daily: Check for seal degradation
• Weekly: Rinse prefilters
• Weekly: Conduct incense smoke test to track improvement
• Monthly: Full visual inspection
• Month 6: Plan HEPA filter replacement (₹3,499)

How to Test (Without Professional Equipment)

Testing Philosophy

• Goal: Verify system sealing and confirm airflow without damaging filters
• No AQI monitors needed in initial stages, unless you explicitly want numbers
• Proxy methods are fairly accurate as particle counters cost ₹5,000+ and professional ones even more
• If you WANT numerical validation: partner with someone who has PM2.5 monitor, do standardized test protocol

Test 1: Sealing Integrity (CRITICAL FIRST)

Incense Smoke Test (Recommended Method)

1. Setup: Light incense stick outside sealed cube
2. Baseline: Note how long smoke dissipates naturally (typical 8-10 minutes)
3. With Fan OFF: Light incense inside room, observe baseline clearance time
4. With Fan ON (LOW): Light incense, turn fan to LOW, observe smoke path
   • Should move toward intake (coarse mesh face)
   • Should NOT escape from any other face/edge/seam
5. With Fan ON (HIGH): Repeat, look for any visible smoke leaks
6. Mark & Reseal: Any visible leaks get marked with tape
7. Repeat: Add foam/tape to marked areas, retest until no visible leaks

Hand Airflow Test (Verification)

1. Place hand near each edge/seam when fan running HIGH
2. Feel for outward air rush (indicates leak)
3. Seal detected leaks immediately

Pressure Test (Quick Check)

1. Seal cube completely (all openings closed temporarily)
2. Seal fan outlet (cloth/tape)
3. Run fan for 5 seconds
4. Cube should feel pressurized (slight outward push when you touch it)
5. If pressure escapes slowly, major leak present (reseal)

Test 2: Filter Performance (WITHOUT AQI Monitor)

Incense Clearing Time Tracking

• Week 1: Baseline (8-10 min without purifier)
• Week 2-4: With purifier ON (should be 2-4 min)
• Expected improvement: 50-75% faster clearance
• Track over months: Should remain consistent if prefilters kept clean

Dust Accumulation Test (Monthly)

1. Place white cloth on horizontal surface in room
2. Mark position
3. Run purifier 24 hours, then OFF 24 hours (control)
4. Compare dust accumulation
5. Purifier-ON surface should have 50-70% less dust

Visual Room Observations (No Equipment)

• Air feels less "heavy" after 30-40 minutes of operation, noticeable within 20m room size is similar to mine. ~99 sqft
• Breathing easier within overnight (10 hrs continuous)
• Dust particles less visible in sunlight beams
• Odor perception decreases
• Respiratory improvement within days

⚠️ SEALING DISCLAIMER

"Do NOT use filters during initial sealing tests. Why? Incense particles can clog new HEPA media. Test sealing with fan intake OPEN (no filters in place) first. Once sealing verified, install filters."

Conclusion: Reiteration

Why This Matters

• Commercial purifiers: ₹16,000+ for 150-250 CFM, same 5-year cost as your DIY
• Your DIY: ₹5,000-7,000 for 550-900 CFM = 5-6x better performance
• Not about attracting users—about providing practical solution for emergency AQI conditions
• This is repurposed materials + low-cost + high-performance—exactly what vulnerable populations need

When to Consider This

• During extreme AQI (999+ AQI events, October-February in Delhi)
• If commercial purifiers unaffordable
• If you have repurposed fan available
• As EMERGENCY response, not permanent solution

When NOT to Pursue This

• If genuine HEPA filters unavailable (don't compromise)
• If budget extremely tight and other basic needs unmet (use ventilation instead)
• If you already own adequate commercial purifier (optimize it instead)

Use → Improve → Share Philosophy

1. Build it: Deploy prototype in your home
2. Monitor it: Track performance over 1-2 months
3. Share results: Post performance data, learnings, failures
4. Iterate: Get feedback, refine design, publish v2.0

Final Recommendation

"If you build this system, eventually upgrade to a commercial purifier when financially capable. This DIY is EMERGENCY bridge solution. Long-term health requires commercial-grade equipment. Use this now, commit to upgrade later."

Future Improvements & Next Steps

Future Enhancement: Activated Carbon Grid (Secondary)

• Why not now: Delhi is 99% PM2.5; carbon is secondary
• When to add: Months 3-6, after validating HEPA performance
• Specification: 30-50mm thick granular activated carbon layer
• Cost: ₹1,400-1,800 (one-time investment)
• Performance: 70-90% VOC removal when implemented correctly
• Trade-off: 15-30% CFM reduction (acceptable at scale)

Action items for future:

• Contact IndiasMart bulk carbon suppliers for minimal pricing
• Request samples from 2-3 suppliers
• Negotiate bulk discount if building 5+ units
• Test carbon layer placement: upstream of HEPA (reduces large dust reaching HEPA)

Community Validation & Surveying

• Your survey form: Collect air quality monitor feedback from builders
• Standardized test protocol: Room dimensions, initial PM2.5, CFM calculation
• Crowdsource validation: Real-world performance across Delhi neighborhoods
• Publish findings: Post aggregate results (50+ units built, average ACH, user satisfaction)

Upgrade Path

• Month 1-3: DIY purifier operation, gather data
• Month 4-6: Decide on activated carbon layer
• Month 6+: If satisfied performance, upgrade to commercial unit alongside DIY
• Goal: Transition to commercial purifier as financial capability increases

Resources & Further Reading

• Coway HEPA specifications: [link]
• Delhi AQI monitoring: [link to aqi.in]
• HEPA filter standards: ISO 11184 (99.97% @ 0.3µm definition)
• Crompton fan datasheets: [link]

Photo/Video References (For Visual Enhancement)

Required Visuals (For Blog)

1. Hero Image: Assembled DIY purifier (front view, clean white background)
2. Blender Render: 3D cross-section showing filter stack (intake → exhaust)
3. BOM Flat-lay: All components laid out (fan, HEPA, mesh, gaskets, etc.)
4. Assembly Process: 4-6 step photos (Day 1 box cutting, Day 3 HEPA mounting, Day 4 fan installation, etc.)
5. Sealing Test: Incense smoke visible being drawn into intake
6. Comparison Chart: DIY vs. Coway vs. IQAir (visual comparison)

Video Suggestions (Optional)

• 60-second assembly timelapse
• Incense smoke test demonstration
• Before/after room visibility comparison

Good luck with final photo/video!