Overview
The investigation involved evaluating six prototypes of PAPR and HEPA buggies. The prototypes ranged from including 1–2 children, using PAPR devices or two different sized HEPA filters, and different types of strollers and rain covers. The goal was to showcase different combinations that may be of interest to families. The investigator aimed to summarize strengths and weaknesses, air flow metrics, sound intensity, and safety.
Buggy Models
The investigation reports on six models of PAPR and HEPA buggies (Fig. 2). The PAPR buggies included the twin car seat buggy (Model 1), a similar version for a single child in a rain-covered car seat stroller (Model 2), a single-child rain-covered baby bassinet stroller (Model 3), and a single-toddler upright seated rain-covered stroller (Model 4). The HEPA versions used a small HEPA filter to provide clean air to two babies in car seats covered by a giant rain cover (Model 5), or one large HEPA filter for one child (Model 6), thus, covering a range of tradeoffs.
Each buggy is assembled with three main supplies as depicted in Fig. 2. These include a stroller, a seat (either built into the stroller, a detachable car seat, or a detachable infant bassinet), and an air cleaner (PAPR or HEPA). The PAPR device was a Trudsafe Powered Air Pump for Respirator. The HEPA filters tested were a small RENPHO RP-AP068W and a large AirTheReal AGH 550. The PAPR is self-powered after charged, and the HEPA filters require a portable power station. All supplies are noted in Table 1. Although the air filters are somewhat hidden within the buggies, the final pane of Fig. 2 shows a closer view of each item. Note that consumers have many alternatives for strollers, car seats, bassinets, rain covers, PAPR, HEPA, and power stations. The investigator encourages future researchers and parents to use supplies on hand and engage in pragmatic replications (also called, “extensions,” “conceptual replications” or “constructive replications”), rather than a direct replication using the identical but arbitrary parts in Table 1.
Table 1
Guide to Products and Parts for PAPR and HEPA Buggies
Testing Equipment |
CADR • Testo 405i hot-wire anemometer ($106), https://www.amazon.com/gp/product/B018VO5GI2/ Sound Intensity, Decibel Meter • RisePRO decibel meter ($20), https://www.amazon.com/gp/product/B01EZZ8B5Q Air Quality, CO2 Monitor • Aranet4 ($249), https://www.amazon.com/gp/product/B07YY7BH2W |
Model 1 |
Stroller • Joovi Twin Roo + frame ($30 used on Craigslist) • Chicco KeyFit 30 car sears ($179 each), https://www.amazon.com/Rear-Facing-Infants-Compatible-Chicco-Strollers/dp/B07MLW6ZSQ/ Rain Cover • Sasha rain and wind cover ($33 each), https://www.amazon.com/gp/product/B07C9JQ5P8/ PAPR with filters • Trudsafe Powered Air Pump for Respirator ($110 each), https://www.amazon.com/gp/product/B09NNKHGT7 • User can purchase non-Trudsafe name-brand 3M filters ($26 for 2 filters), https://www.amazon.com/gp/product/B009POHLRC • If using 3M filters, 3M 701 Black/Orange Filter Adapters ($23 for 2 adapters) are needed, which are very difficult to set up but viable (consider alternatives), https://www.amazon.com/gp/product/B004RH1RXG |
Model 2 |
Stroller • Chicco KeyFit Liteway Stroller ($30 used on Facebook) • Car seat the same as Model 1 Rain Cover • Same as Model 1 PAPR • Same as Model 1 |
Model 3 |
Stroller • UppaBaby Bassinet Stroller (very old model, acquired used) Rain Cover • The investigator does not use this model presently, so parents will need to shop for their own recommendations on bassinet rain covers PAPR • Same as Models 1–2 |
Model 4 |
Stroller • Chicco Liteway Stroller ($30 on Facebook) Rain Cover • Unknown, unbranded and old PAPR • Same as Models 1–3 |
Model 5 |
Stroller • Same as Model 1 Rain Cover • Ezkindheit Double-Stroller Rain Cover ($30), https://www.amazon.com/gp/product/B09CGLL4DR/ HEPA filter • RENPHO RP-AP068W ($55), https://www.amazon.com/gp/product/B07Q3DWSTX Power Supply • There are many portable power stations in the $70–100 range that allow 2 or 3-prong outlets. Due to living in a hurricane zone with a recent prolonged power outage and evacuation, the investigator bought a more powerful version that is beyond what most families would need, the Westinghouse iGen300s ($239), https://www.amazon.com/gp/product/B08DSHCK1C |
Model 6 |
Stroller • Same as Models 1 and 5 Rain Cover • Same as Model 5 HEPA filter • AirTheReal AGH 550 ($220), https://www.projectn95.org/products/hepa-filter-agh550-black-air-purifier Power Supply • Same as Model 5 |
parents to use supplies on hand and engage in pragmatic replications (also called, “extensions,” “conceptual replications” or “constructive replications”), rather than a direct replication using the identical but arbitrary parts in Table 1.
Supply price estimates are shown in U.S. dollars (USD). Approximate exchange rates are that $100 (USD) = 93.8 € = 82.7 £ = 13,282.8 ¥.
Air Flow
The evaluation assessed three metrics of air flow. The first metric was the clean air delivery rate (CADR) for each device, the rate at which it pumps clean air. The PAPR manufacturer did not supply a CADR estimate, so the investigator measured it using a Testo 405i hot-wire anemometer, achieving values similar to those manufacturers of other PAPRs report. The HEPA manufacturers did provide CADR estimates, which the investigator confirmed via the anemometer.
Second, the investigator estimated the number of air changes per hour (ACH) within the enclosed area of each model, which can be thought of as the speed of cleaning the air within a given sized volume. These estimates required manually measuring the interior dimensions of each model, often irregular, and using trigonometry to estimate area and compute volume. Rounded corners were treated as larger polygons to err toward overestimating volume and, thus, underestimating ACH. ACH was computed using the standard formula [33], noted in Table 2. Many engineers and retailers use the units of “cfm” or ft3/minute, so statistics include both Imperial and SI units. Table 3 provides a spreadsheet of spatial volume (right column) by CADR (top row) so that parents less familiar with engineering equations can quickly estimate ACH (Imperial and SI units provided). They would just need to calculate the approximate spatial volume (or a stroller enclosure, room, or other place) and get the CADR estimate from the manufacturer.
Third, given that CADR and ACH are unfamiliar acronyms to many parents who may benefit from this article, the investigator also computer a final metric, called “Operating Room
Table 2
Formulas for Converting Air Filter Clean Air Delivery Rate (CADR) to Air Changes Per Hour (ACH) and Operation Room Equivalents (ORE)
ACH in Imperial Units |
CADR of PAPR or HEPA in ft3/minute (also called “cfm”) | X 60 minutes in an hour | ÷ Room or Enclosure Size in ft3 | = ACH |
ACH in SI Units |
CADR of PAPR or HEPA in m3/minute | X 60 minutes in an hour | ÷ Room or Enclosure Size in m3 | = ACH |
Operating Room Equivalents | | | |
ACH | ÷ 15 ACH of an Operating Room | = Operating Room Equivalents | |
Table 3
Chart for Converting Air Filter Clean Air Delivery Rate (CADR) and Room (or Rain Cover Enclosure) Size into Air Changes Per Hour (ACH), using SI or Imperial Units
SI Units |
| CADR of PAPR or HEPA Air Filter (m3/minute) |
Room or Buggy Size (m3) | 0.1 | 0.25 | 0.5 | 0.75 | 1 | 2 | 3 | 4 | 5 | 10 | 15 | 20 | 25 | 30 |
0.03 | 200 | 500 | 1000 | 1500 | 2000 | 4000 | 6000 | 8000 | 10000 | 20000 | 30000 | 40000 | 50000 | 60000 |
0.06 | 100 | 250 | 500 | 750 | 1000 | 2000 | 3000 | 4000 | 5000 | 10000 | 15000 | 20000 | 25000 | 30000 |
0.09 | 67 | 167 | 333 | 500 | 667 | 1333 | 2000 | 2667 | 3333 | 6667 | 10000 | 13333 | 16667 | 20000 |
0.12 | 50 | 125 | 250 | 375 | 500 | 1000 | 1500 | 2000 | 2500 | 5000 | 7500 | 10000 | 12500 | 15000 |
0.15 | 40 | 100 | 200 | 300 | 400 | 800 | 1200 | 1600 | 2000 | 4000 | 6000 | 8000 | 10000 | 12000 |
0.18 | 33 | 83 | 167 | 250 | 333 | 667 | 1000 | 1333 | 1667 | 3333 | 5000 | 6667 | 8333 | 10000 |
0.21 | 29 | 71 | 143 | 214 | 286 | 571 | 857 | 1143 | 1429 | 2857 | 4286 | 5714 | 7143 | 8571 |
0.24 | 25 | 63 | 125 | 188 | 250 | 500 | 750 | 1000 | 1250 | 2500 | 3750 | 5000 | 6250 | 7500 |
0.27 | 22 | 56 | 111 | 167 | 222 | 444 | 667 | 889 | 1111 | 2222 | 3333 | 4444 | 5556 | 6667 |
0.30 | 20 | 50 | 100 | 150 | 200 | 400 | 600 | 800 | 1000 | 2000 | 3000 | 4000 | 5000 | 6000 |
0.33 | 18 | 45 | 91 | 136 | 182 | 364 | 545 | 727 | 909 | 1818 | 2727 | 3636 | 4545 | 5455 |
0.36 | 17 | 42 | 83 | 125 | 167 | 333 | 500 | 667 | 833 | 1667 | 2500 | 3333 | 4167 | 5000 |
0.39 | 15 | 38 | 77 | 115 | 154 | 308 | 462 | 615 | 769 | 1538 | 2308 | 3077 | 3846 | 4615 |
0.42 | 14 | 36 | 71 | 107 | 143 | 286 | 429 | 571 | 714 | 1429 | 2143 | 2857 | 3571 | 4286 |
0.45 | 13 | 33 | 67 | 100 | 133 | 267 | 400 | 533 | 667 | 1333 | 2000 | 2667 | 3333 | 4000 |
0.48 | 13 | 31 | 63 | 94 | 125 | 250 | 375 | 500 | 625 | 1250 | 1875 | 2500 | 3125 | 3750 |
0.51 | 12 | 29 | 59 | 88 | 118 | 235 | 353 | 471 | 588 | 1176 | 1765 | 2353 | 2941 | 3529 |
0.54 | 11 | 28 | 56 | 83 | 111 | 222 | 333 | 444 | 556 | 1111 | 1667 | 2222 | 2778 | 3333 |
0.57 | 11 | 26 | 53 | 79 | 105 | 211 | 316 | 421 | 526 | 1053 | 1579 | 2105 | 2632 | 3158 |
0.60 | 10 | 25 | 50 | 75 | 100 | 200 | 300 | 400 | 500 | 1000 | 1500 | 2000 | 2500 | 3000 |
0.63 | 10 | 24 | 48 | 71 | 95 | 190 | 286 | 381 | 476 | 952 | 1429 | 1905 | 2381 | 2857 |
0.66 | 9 | 23 | 45 | 68 | 91 | 182 | 273 | 364 | 455 | 909 | 1364 | 1818 | 2273 | 2727 |
0.69 | 9 | 22 | 43 | 65 | 87 | 174 | 261 | 348 | 435 | 870 | 1304 | 1739 | 2174 | 2609 |
0.72 | 8 | 21 | 42 | 63 | 83 | 167 | 250 | 333 | 417 | 833 | 1250 | 1667 | 2083 | 2500 |
0.75 | 8 | 20 | 40 | 60 | 80 | 160 | 240 | 320 | 400 | 800 | 1200 | 1600 | 2000 | 2400 |
0.78 | 8 | 19 | 38 | 58 | 77 | 154 | 231 | 308 | 385 | 769 | 1154 | 1538 | 1923 | 2308 |
0.81 | 7 | 19 | 37 | 56 | 74 | 148 | 222 | 296 | 370 | 741 | 1111 | 1481 | 1852 | 2222 |
0.84 | 7 | 18 | 36 | 54 | 71 | 143 | 214 | 286 | 357 | 714 | 1071 | 1429 | 1786 | 2143 |
0.87 | 7 | 17 | 34 | 52 | 69 | 138 | 207 | 276 | 345 | 690 | 1034 | 1379 | 1724 | 2069 |
0.90 | 7 | 17 | 33 | 50 | 67 | 133 | 200 | 267 | 333 | 667 | 1000 | 1333 | 1667 | 2000 |
1.00 | 6 | 15 | 30 | 45 | 60 | 120 | 180 | 240 | 300 | 600 | 900 | 1200 | 1500 | 1800 |
2.00 | 3 | 8 | 15 | 23 | 30 | 60 | 90 | 120 | 150 | 300 | 450 | 600 | 750 | 900 |
3.00 | 2 | 5 | 10 | 15 | 20 | 40 | 60 | 80 | 100 | 200 | 300 | 400 | 500 | 600 |
4.00 | 2 | 4 | 8 | 11 | 15 | 30 | 45 | 60 | 75 | 150 | 225 | 300 | 375 | 450 |
5.00 | 1 | 3 | 6 | 9 | 12 | 24 | 36 | 48 | 60 | 120 | 180 | 240 | 300 | 360 |
6.00 | 1 | 3 | 5 | 8 | 10 | 20 | 30 | 40 | 50 | 100 | 150 | 200 | 250 | 300 |
7.00 | 1 | 2 | 4 | 6 | 9 | 17 | 26 | 34 | 43 | 86 | 129 | 171 | 214 | 257 |
8.00 | 1 | 2 | 4 | 6 | 8 | 15 | 23 | 30 | 38 | 75 | 113 | 150 | 188 | 225 |
9.00 | 1 | 2 | 3 | 5 | 7 | 13 | 20 | 27 | 33 | 67 | 100 | 133 | 167 | 200 |
10.00 | 1 | 2 | 3 | 5 | 6 | 12 | 18 | 24 | 30 | 60 | 90 | 120 | 150 | 180 |
20.00 | 0 | 1 | 2 | 2 | 3 | 6 | 9 | 12 | 15 | 30 | 45 | 60 | 75 | 90 |
30.00 | 0 | 1 | 1 | 2 | 2 | 4 | 6 | 8 | 10 | 20 | 30 | 40 | 50 | 60 |
40.00 | 0 | 0 | 1 | 1 | 2 | 3 | 5 | 6 | 8 | 15 | 23 | 30 | 38 | 45 |
50.00 | 0 | 0 | 1 | 1 | 1 | 2 | 4 | 5 | 6 | 12 | 18 | 24 | 30 | 36 |
100.00 | 0 | 0 | 0 | 0 | 1 | 1 | 2 | 2 | 3 | 6 | 9 | 12 | 15 | 18 |
Imperial Units |
| CADR of PAPR or HEPA Air Filter (ft3/minute) |
Room or Buggy Size (ft3) | 5 | 10 | 25 | 50 | 75 | 100 | 150 | 200 | 250 | 300 | 400 | 500 | 750 | 1000 |
1 | 300 | 600 | 1500 | 3000 | 4500 | 6000 | 9000 | 12000 | 15000 | 18000 | 24000 | 30000 | 45000 | 60000 |
2 | 150 | 300 | 750 | 1500 | 2250 | 3000 | 4500 | 6000 | 7500 | 9000 | 12000 | 15000 | 22500 | 30000 |
3 | 100 | 200 | 500 | 1000 | 1500 | 2000 | 3000 | 4000 | 5000 | 6000 | 8000 | 10000 | 15000 | 20000 |
4 | 75 | 150 | 375 | 750 | 1125 | 1500 | 2250 | 3000 | 3750 | 4500 | 6000 | 7500 | 11250 | 15000 |
5 | 60 | 120 | 300 | 600 | 900 | 1200 | 1800 | 2400 | 3000 | 3600 | 4800 | 6000 | 9000 | 12000 |
6 | 50 | 100 | 250 | 500 | 750 | 1000 | 1500 | 2000 | 2500 | 3000 | 4000 | 5000 | 7500 | 10000 |
7 | 43 | 86 | 214 | 429 | 643 | 857 | 1286 | 1714 | 2143 | 2571 | 3429 | 4286 | 6429 | 8571 |
8 | 38 | 75 | 188 | 375 | 563 | 750 | 1125 | 1500 | 1875 | 2250 | 3000 | 3750 | 5625 | 7500 |
9 | 33 | 67 | 167 | 333 | 500 | 667 | 1000 | 1333 | 1667 | 2000 | 2667 | 3333 | 5000 | 6667 |
10 | 30 | 60 | 150 | 300 | 450 | 600 | 900 | 1200 | 1500 | 1800 | 2400 | 3000 | 4500 | 6000 |
11 | 27 | 55 | 136 | 273 | 409 | 545 | 818 | 1091 | 1364 | 1636 | 2182 | 2727 | 4091 | 5455 |
12 | 25 | 50 | 125 | 250 | 375 | 500 | 750 | 1000 | 1250 | 1500 | 2000 | 2500 | 3750 | 5000 |
13 | 23 | 46 | 115 | 231 | 346 | 462 | 692 | 923 | 1154 | 1385 | 1846 | 2308 | 3462 | 4615 |
14 | 21 | 43 | 107 | 214 | 321 | 429 | 643 | 857 | 1071 | 1286 | 1714 | 2143 | 3214 | 4286 |
15 | 20 | 40 | 100 | 200 | 300 | 400 | 600 | 800 | 1000 | 1200 | 1600 | 2000 | 3000 | 4000 |
16 | 19 | 38 | 94 | 188 | 281 | 375 | 563 | 750 | 938 | 1125 | 1500 | 1875 | 2813 | 3750 |
17 | 18 | 35 | 88 | 176 | 265 | 353 | 529 | 706 | 882 | 1059 | 1412 | 1765 | 2647 | 3529 |
18 | 17 | 33 | 83 | 167 | 250 | 333 | 500 | 667 | 833 | 1000 | 1333 | 1667 | 2500 | 3333 |
19 | 16 | 32 | 79 | 158 | 237 | 316 | 474 | 632 | 789 | 947 | 1263 | 1579 | 2368 | 3158 |
20 | 15 | 30 | 75 | 150 | 225 | 300 | 450 | 600 | 750 | 900 | 1200 | 1500 | 2250 | 3000 |
21 | 14 | 29 | 71 | 143 | 214 | 286 | 429 | 571 | 714 | 857 | 1143 | 1429 | 2143 | 2857 |
22 | 14 | 27 | 68 | 136 | 205 | 273 | 409 | 545 | 682 | 818 | 1091 | 1364 | 2045 | 2727 |
23 | 13 | 26 | 65 | 130 | 196 | 261 | 391 | 522 | 652 | 783 | 1043 | 1304 | 1957 | 2609 |
24 | 13 | 25 | 63 | 125 | 188 | 250 | 375 | 500 | 625 | 750 | 1000 | 1250 | 1875 | 2500 |
25 | 12 | 24 | 60 | 120 | 180 | 240 | 360 | 480 | 600 | 720 | 960 | 1200 | 1800 | 2400 |
26 | 12 | 23 | 58 | 115 | 173 | 231 | 346 | 462 | 577 | 692 | 923 | 1154 | 1731 | 2308 |
27 | 11 | 22 | 56 | 111 | 167 | 222 | 333 | 444 | 556 | 667 | 889 | 1111 | 1667 | 2222 |
28 | 11 | 21 | 54 | 107 | 161 | 214 | 321 | 429 | 536 | 643 | 857 | 1071 | 1607 | 2143 |
29 | 10 | 21 | 52 | 103 | 155 | 207 | 310 | 414 | 517 | 621 | 828 | 1034 | 1552 | 2069 |
30 | 10 | 20 | 50 | 100 | 150 | 200 | 300 | 400 | 500 | 600 | 800 | 1000 | 1500 | 2000 |
40 | 8 | 15 | 38 | 75 | 113 | 150 | 225 | 300 | 375 | 450 | 600 | 750 | 1125 | 1500 |
50 | 6 | 12 | 30 | 60 | 90 | 120 | 180 | 240 | 300 | 360 | 480 | 600 | 900 | 1200 |
60 | 5 | 10 | 25 | 50 | 75 | 100 | 150 | 200 | 250 | 300 | 400 | 500 | 750 | 1000 |
70 | 4 | 9 | 21 | 43 | 64 | 86 | 129 | 171 | 214 | 257 | 343 | 429 | 643 | 857 |
80 | 4 | 8 | 19 | 38 | 56 | 75 | 113 | 150 | 188 | 225 | 300 | 375 | 563 | 750 |
90 | 3 | 7 | 17 | 33 | 50 | 67 | 100 | 133 | 167 | 200 | 267 | 333 | 500 | 667 |
100 | 3 | 6 | 15 | 30 | 45 | 60 | 90 | 120 | 150 | 180 | 240 | 300 | 450 | 600 |
200 | 2 | 3 | 8 | 15 | 23 | 30 | 45 | 60 | 75 | 90 | 120 | 150 | 225 | 300 |
300 | 1 | 2 | 5 | 10 | 15 | 20 | 30 | 40 | 50 | 60 | 80 | 100 | 150 | 200 |
400 | 1 | 2 | 4 | 8 | 11 | 15 | 23 | 30 | 38 | 45 | 60 | 75 | 113 | 150 |
500 | 1 | 1 | 3 | 6 | 9 | 12 | 18 | 24 | 30 | 36 | 48 | 60 | 90 | 120 |
600 | 1 | 1 | 3 | 5 | 8 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 75 | 100 |
700 | 0 | 1 | 2 | 4 | 6 | 9 | 13 | 17 | 21 | 26 | 34 | 43 | 64 | 86 |
800 | 0 | 1 | 2 | 4 | 6 | 8 | 11 | 15 | 19 | 23 | 30 | 38 | 56 | 75 |
900 | 0 | 1 | 2 | 3 | 5 | 7 | 10 | 13 | 17 | 20 | 27 | 33 | 50 | 67 |
1,000 | 0 | 1 | 2 | 3 | 5 | 6 | 9 | 12 | 15 | 18 | 24 | 30 | 45 | 60 |
2,000 | 0 | 0 | 1 | 2 | 2 | 3 | 5 | 6 | 8 | 9 | 12 | 15 | 23 | 30 |
3,000 | 0 | 0 | 1 | 1 | 2 | 2 | 3 | 4 | 5 | 6 | 8 | 10 | 15 | 20 |
4,000 | 0 | 0 | 0 | 1 | 1 | 2 | 2 | 3 | 4 | 5 | 6 | 8 | 11 | 15 |
5,000 | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 | 6 | 9 | 12 |
6,000 | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 8 | 10 |
7,000 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 6 | 9 |
8,000 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 2 | 2 | 3 | 4 | 6 | 8 |
9,000 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 2 | 2 | 3 | 3 | 5 | 7 |
10,000 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 2 | 2 | 2 | 3 | 5 | 6 |
Note. The sizes in the left column can be used for the interior enclosures of buggies or room sizes. Calculate the volume of rectangular prisms like rooms as the product of the dimensions (i.e., length X width X height), or use trigonometry to calculate the area of other polygons (e.g., side of an enclosed stroller) and multiply it by the remaining dimension. Contact the corresponding author for any help. The CADR values can be used for PAPR devices or HEPA filters. If buying a HEPA filter, the manufacturer may provide the CADR usually listed in cfm (cubic feet per minute) units, but note that this reflects the highest and loudest setting. HEPA filters often need to be set to one setting lower for tolerable volume, so a useful practice may be to buy HEPA filters with an advertised CADR 150% of the level desired. The ACH estimates in this table can be converted to “Operating Room Equivalents” by dividing by 15.
Equivalents.” The U.S. Centers for Disease Control and Prevention (CDC) stipulates that operating rooms should maintain at least 15 ACH [34]. Thus, the investigator also divided ACH by 15 to yield Operating Room Equivalents (see Table 2). For example, an ACH of 45 would indicate 3 Operating Room Equivalents or cleaning the air at 3 times the CDC operating room standard.
Sound Intensity
A RisePRO decibel meter was used to estimate sound intensity for each model. Average measurements were recorded from 1.83 m (6 ft) away within a quiet room, subtracting ambient sound intensity using a standard log scale decibel calculator.
Safety
Although commercially-sold stroller rain covers have vents to prevent the build-up of poor air quality or asphyxiation, cautious readers may appreciate being able to cite additional testing. Asphyxiation risk would be higher the smaller the enclosed volume, so the investigator evaluated Model 2 for CO2 buildup during use via an Aranet4 CO2 monitor. The investigator recorded ambient CO2 levels, CO2 levels in the uncovered car seat with baby present, and CO2 levels in the covered car seat with baby present and PAPR running, reporting average values once CO2 levels stabilized (plateaued) under each situation. Recordings within the car seat were 12 inches away from a 2-month-old’s mouth. Reference levels are also reported.