Thermacell
Thermacell Patio Shield MR300 Mosquito Repeller
Spatial Device · EPA-registered spatial repellent device
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Pros
- Strong landing/bite reduction in field trials (70–92%)
- Protects a real zone (about 15 ft in still air)
- EPA-registered device
- Active ingredient concentration disclosed
Cons
- Protects only the treated zone, and effectiveness drops sharply in wind or open air
- Highly toxic to fish and aquatic life — keep well away from water
- Pyrethroid vapor — keep cats away and never run it in an enclosed space
The full review
Fuel-powered area repeller that uses a butane cartridge to heat an allethrin repellent mat, releasing a vapor that protects roughly a 15-foot zone around a patio or campsite. The long-running, widely sold Thermacell design, it needs no batteries or charging. Effectiveness is best in calm, sheltered air and drops off in wind or at the edge of the zone.
Scorecard
Expand any pillar to see exactly why it scored what it did.
Effectiveness45%77This is an area device, not applied to skin: published field trials report roughly 70–92% fewer mosquito landings or bites, over about a 15 ft zone. Scored 60% on that reduction and 40% on how much space it protects, so a larger zone counts for real. Reduction figures come from controlled or semi-field trials, not backyard conditions. Real-world protection drops sharply in wind and open air, so this is scored with lower confidence.
This is an area device, not applied to skin: published field trials report roughly 70–92% fewer mosquito landings or bites, over about a 15 ft zone. Scored 60% on that reduction and 40% on how much space it protects, so a larger zone counts for real. Reduction figures come from controlled or semi-field trials, not backyard conditions. Real-world protection drops sharply in wind and open air, so this is scored with lower confidence.
Evidence & honest claims25%63Allethrin is well-supported by published evidence, weighted by how close its concentration is to the studied effective dose (base 56). Of 4 marketing claims audited: 1 strong, 3 moderate, 0 weak, 0 unsupported (+7).
Allethrin is well-supported by published evidence, weighted by how close its concentration is to the studied effective dose (base 56). Of 4 marketing claims audited: 1 strong, 3 moderate, 0 weak, 0 unsupported (+7).
Safety15%60This is an area device, not applied to skin, so dermal risk does not apply. Scored on moderate inhalation risk from the vapor (−18); high toxicity to fish and aquatic life (−22). Use it outdoors in the open air only, keep cats away. Keep it well away from ponds, aquariums, and water features.
This is an area device, not applied to skin, so dermal risk does not apply. Scored on moderate inhalation risk from the vapor (−18); high toxicity to fish and aquatic life (−22). Use it outdoors in the open air only, keep cats away. Keep it well away from ponds, aquariums, and water features.
Transparency15%75This product publishes an ingredient list (+20); discloses 100% of active concentrations (+40); discloses 100% of all ingredient concentrations (+15); inert ingredients are not fully accounted for (0).
This product publishes an ingredient list (+20); discloses 100% of active concentrations (+40); discloses 100% of all ingredient concentrations (+15); inert ingredients are not fully accounted for (0).
Every pillar is scored from published rules. Read how we score.
Coverage & effectiveness
This is an area device: it protects a zone around it rather than your skin. Effectiveness is the published reduction in mosquito landings or bites. Real-world protection is best in still air and drops in wind or open space.
Mosquitoes
EstimatedModerate- Protected zone
- ~15 ft zone
- Fewer bites
- 70–92%
Field trials of allethrin Thermacell units have measured around 90 percent fewer bites in favorable conditions, with one Turkey field trial reporting about 92 percent. Protection falls off in wind and near the edge of the zone, so results vary with weather and airflow.
Ingredient disclosure
This product publishes an ingredient list (+20); discloses 100% of active concentrations (+40); discloses 100% of all ingredient concentrations (+15); inert ingredients are not fully accounted for (0).
Only active ingredients are disclosed. The full ingredient list (inerts/carriers) is not published, so this may not be the complete formula.
- AllethrinActive
Active repellent · 21.97%
Claims audit
What the marketing says, versus what the evidence supports.
“Creates a 15-foot zone of mosquito protection”
EfficacyModerateBest-case still-air figure; wind reduces the effective range.
“EPA-registered allethrin repeller with a long track record”
SafetyModerateDevice is EPA-registered (EPA Reg. No. 71910-2); avoid breathing the vapor directly and use outdoors only.
“DEET-free, scent-free, no spray and no mess”
Deet FreeStrongActive is allethrin, not DEET.
“Up to 12 hours of protection per fuel cartridge”
DurationModerateFuel and mat runtimes per manufacturer; mats must be swapped as they fade.
Safe around dogs & cats?
Worst case from this product’s active ingredients. Do not apply this or any human repellent to your pet.
Mainly from Allethrin.
Not veterinary advice. Full guide to repellents around pets →