Firebrats need warmth and moisture to survive, which means the most effective natural strategy is making your home inhospitable to them. These small, fast-moving insects thrive in hot, humid spots like water heater closets, behind ovens, and near furnace ducts. By cutting off their moisture, food, and hiding places, you can eliminate an infestation without chemical pesticides.
Make Sure You’re Dealing With Firebrats
Firebrats are often confused with their close relative, the silverfish, and the distinction matters because they prefer different environments. Both are about half an inch long, wingless, and teardrop-shaped with three thin tail-like appendages at the rear and two long antennae at the front. The key visual difference is color: silverfish are shiny silver or pearl gray, while firebrats have a mottled gray-brown pattern that looks almost speckled.
The bigger clue is where you find them. Silverfish prefer cool, damp areas like basements and bathrooms. Firebrats seek out heat. If you’re spotting these insects near your oven, furnace, hot water heater, or heating pipes, you almost certainly have firebrats. They’re nocturnal and extremely fast, so you may notice damage to paper goods or starchy materials before you ever see the insect itself.
Drop the Humidity Below 50 Percent
This is the single most important step. Firebrat females require humidity of 50 percent or higher to reproduce, and they lay only about 50 eggs in a lifetime. That low reproductive rate means even a modest drop in humidity can stop a population from sustaining itself. If you keep the relative humidity in problem areas consistently below 50 percent, the colony will shrink and eventually die out.
Use a dehumidifier in enclosed rooms where firebrats have been spotted. Fix leaky pipes, especially around water heaters and in utility closets. Improve ventilation in bathrooms and laundry rooms by running exhaust fans during and after showers or dryer use. In attics and crawl spaces, adding ventilation or vapor barriers can make a significant difference. A cheap hygrometer (humidity gauge) placed near problem areas will tell you whether your efforts are working.
Eliminate Their Food Sources
Firebrats eat an impressively wide range of household materials. They’ve been observed feeding on glue, wallpaper paste, book bindings, paper, photographs, starch in clothing, cotton, linen, rayon fabrics, wheat flour, cereals, dried meats, leather, and even dead insects. Anything starchy, sugary, or protein-rich is fair game.
Store flour, cereals, and other dry goods in sealed glass or hard plastic containers rather than leaving them in cardboard boxes or paper bags. Move old newspapers, magazines, and cardboard out of warm storage areas. If you have books, photographs, or important documents in a room near a heat source, consider relocating them or storing them in sealed plastic bins. Starched clothing stored in closets near hot water heaters or furnaces should go into sealed garment bags or be moved to cooler areas of the house.
Apply Diatomaceous Earth in Key Spots
Food-grade diatomaceous earth (DE) is one of the most effective natural tools against firebrats. It’s a fine powder made from fossilized algae that works mechanically, not chemically. When firebrats crawl through it, the tiny particles scratch their waxy outer coating and absorb moisture from their bodies, causing them to dehydrate and die. Modified forms of DE have been shown to completely eradicate silverfish (a closely related species) within 10 days in controlled settings.
Apply a thin, even layer of DE along baseboards, behind appliances like ovens and refrigerators, inside utility closets around water heaters, and beneath sinks. The key word is thin: a barely visible dusting is more effective than a thick pile, because firebrats will simply walk around a heavy mound. Focus on cracks and crevices where walls meet floors, around pipe entry points, and along the edges of cabinets.
One important detail: DE works best when dry. Its effectiveness drops dramatically when it gets wet, with some research showing a tenfold reduction in potency when mixed with water. If you’re applying it in a bathroom or near a sink, reapply after any moisture exposure. In naturally humid areas, pair DE with dehumidification for the best results.
Use Simple Homemade Traps
Glass jar traps are a straightforward way to catch and monitor firebrats. Take a small mason jar or similar glass container and wrap the outside with masking tape or fabric tape. This gives firebrats traction to climb up and into the jar, but the smooth glass interior prevents them from climbing back out. Place a small piece of bread, a pinch of flour, or a bit of cereal at the bottom as bait.
Set these traps in the warmest areas of your home, particularly near heat-generating appliances and along walls where you’ve noticed activity. Check and empty them every few days. These traps won’t eliminate an infestation on their own, but they serve two purposes: reducing the population and telling you exactly where the insects are concentrated so you can target those areas with DE and humidity control.
Sticky traps (available at hardware stores as “insect monitors”) placed along baseboards near warm appliances work similarly and require less effort to maintain.
Seal Entry Points and Hiding Spots
Firebrats are flat-bodied and can squeeze into remarkably small gaps. Caulk cracks along baseboards, around pipe penetrations, and where walls meet floors in kitchens, bathrooms, and utility rooms. Pay special attention to the area around your water heater, furnace, and oven, as these warm zones are prime firebrat habitat. Seal gaps around electrical outlets on shared walls with foam gaskets.
Remove clutter from warm areas. Stacked cardboard boxes in a furnace room are essentially a firebrat buffet and apartment complex in one. Replace cardboard storage with sealed plastic bins, and keep storage areas as clean and open as possible so there are fewer places for firebrats to hide and breed.
Use Essential Oils as a Deterrent
Cedar oil, lavender oil, and citrus-based sprays are commonly used as natural repellents for firebrats and silverfish. While these won’t kill firebrats or eliminate an established population, they can discourage insects from returning to treated areas. Mix 10 to 15 drops of cedar or lavender essential oil with water in a spray bottle and apply it along baseboards, in closets, and around bookshelves.
Cedar blocks or sachets placed in storage bins and closets serve a similar purpose and last longer than sprays. These work best as a complement to the more effective strategies above, not as a standalone solution.
Combine Methods for Lasting Results
No single approach will solve a firebrat problem overnight. The most reliable natural strategy layers multiple methods together. Start by identifying where the firebrats are concentrated using traps. Reduce humidity in those areas below 50 percent. Remove or seal up their food sources. Apply diatomaceous earth in cracks and along baseboards. Seal entry points to limit their movement between rooms.
Firebrats reproduce slowly compared to many household pests, so a consistent effort over two to four weeks typically produces noticeable results. If you still see activity after a month of combined measures, the insects likely have a hiding spot you haven’t found, often inside wall voids near heat sources or in insulation around hot water pipes. In those cases, applying DE directly into wall cavities through electrical outlet openings (with the power off) or pipe entry gaps can reach populations you can’t otherwise access.