**Basic Assumptions**

1. Because this is a comparison of HEPA lifespan, I’m not including costs for carbon filters. However, I am including pre-filters because the HEPA lifespan depends on the pre-filter.

2. I’m comparing on the highest speed because (1) Blue Air only provides figures based on the highest speed and (2) the Original DIY test comparison was on its highest setting.

3. Because the Original DIY longevity test was run in approximately 8-hour days, I’m converting all of the longevity figures into 8-hour days.

**Costs**

1. Original DIY

The Original DIY calculations are pretty simple:

140 days/ 80 RMB = .57 RMB per day

.57 RMB * 365 days per year = 208.57 RMB per year

2. Blue Air 203

http://us.blueair.com/product/blueair-203/blueair-203-faqs

Calculating for the Blue Air is tricky because they give the lifespan as 6 months regardless of how many hours you use it per day and what speed it’s on. And according to David Helman from HEPA China, if you leave it plugged in but off, it will still tell you to replace the filters after 6 months.

To get to the bottom of it, I emailed Blue Air and asked how often I should change the filters based on 8 hours a day. Blue Air responded that I should still change it after 6 months and that if I use it for longer, I could damage the motor and void the warranty. Thus, I stuck with the website’s recommendation of 188 days.

Price: The price of the Blue Air HEPA is tough to calculate because, from what I can find, it’s sold in the same box as the carbon. However, I was able to find what I think is just the HEPA on Amazon in the US for $50. That sounds about right, since the HEPA + carbon is 400 RMB on Taobao.

On the day I made the calculation (1/9/2015), Google said $50 USD = 310.63 RMB.

Thus:

310.63 RMB / 188 days

= 1.65228723404255 RMB per day

1.65228723404255 * 365

= 603.084 RMB per year

That puts the Blue Air well above the DIY but below the IQ Air, which makes sense given the relative prices.

If we violate the Blue Air 6-month rule (risk our warranty) and assume it’s actual hours of usage, we could assume that it should be used the 10 hours a day that IQ Air assumes for its filters. If we assume 10 hours a day, the calculation is:

188 * 10hours a day

= 1880

188 * 10 / 8

= 235 # of 8-hour days of usage

310.63 RMB / 235

= 1.32182978723404 RMB per day

1.32182978723404 * 365 days a year

= 482.467 RMB per year

That’s a bit lower, although still more than double the DIY cost.

**3. IQ Air**

For the IQ Air Health Pro Plus, the IQ Air website says only that the HEPA lasts “approx. 4 years (based on average daily usage of 10h on speed 3).” There’s a lot of wiggle room in that estimate, and I’d have to use a lot of assumption to try to convert it to speed 6. Fortunately, an IQ Air North American authorized dealer provided the following figures to David Helman of HEPA China:

*HyperHEPA:*

Speed 1: 41.9 months

Speed 2: 23.5 months

Speed 3: 15.1 months

Speed 4: 11.9 months

Speed 5: 9.7 months

Speed 6: 6.9 months

*PreMax:*

Speed 1: 17.1 months

Speed 2: 9.6 months

Speed 3: 6.2 months

Speed 4: 4.9 months

Speed 5: 4.0 months

Speed 6: 2.8 months

These figures are for 24/7 usage. They are from the North American dealer, so the filters almost surely would not last as long in China, but to be conservative, I’m taking them as a given.

HEPA speed 6:

6.9months * 30 days a month * 24hours a day

= 4968 total hours of usage

4968 / 8 hours a day

= 621 days of use at 8 hours a day

1782 RMB / 621 days

= 2.8695652173913 cost in RMB per day

2.8695652173913 * 365 days a year

= 1047.391 cost in RMB per year

IQ Air pre-filter

Cost 645 RMB

Speed 6:

2.8months * 30days per month * 24hours per day

= 2016

2016 / 8 hours per day

= 252 total days of use (8 hours per day)

645 RMB / 252 days

= 2.55952380952381 RMB per day of use

2.55952380952381 * 365 days

= 934.226 RMB per year of use

Total = 934.23 + 1047.39 = 1981.62 RMB

For comparison, here is the calculation based on speed 3:

HEPA

15.1 * 30 * 24

= 10872

15.1 * 30 * 24 / 8

= 1359

1782 / 1359

= 1.3112582781457

1782 / 1359 * 365

= 478.609 RMB per year

Pre-filter

6.2 * 30 * 24

= 4464

6.2 * 30 * 24 / 8

= 558

645 / 558

= 1.15591397849462 RMB per day

645 / 558 * 365

= 421.908 RMB per year

Cost per year on speed 3: 421.91 + 478.61 = 900.52 RMB per year

Because they’re processing less air, the filters would last longer and thus cost less on speed 3 compared to speed 6. According to the calculations, speed 3 is roughly half the cost of speed 6.

Cost per year:

Speed 3: 900.52 RMB

Speed 6: 1981.62 RMB