Heat Treatment Explained — And Why Eggs Survive Chemicals

Heat kills bed bugs by denaturing protein, and the thermal death point is a curve rather than a single number — temperature and exposure time trade against each other. Sustained 130°F kills every life stage including eggs, which is the one fact that separates thermal remediation from every chemical approach.

That fact is why a treatment costing $400 to $900 per room can be cheaper overall than one costing $270 to $775. This guide is the mechanism behind it: what the heat is doing, what equipment does it, and the four ways it goes wrong.

The mechanism, and why resistance cannot develop

Heat kills insects by denaturing proteins and destabilising cell membranes. Enzymes unfold, stop working, and the insect dies of systemic metabolic failure rather than of poisoning.

This is a physical process, not a toxicological one, and that distinction carries the entire practical advantage. Resistance to an insecticide develops because some individuals carry a mutation — a modified sodium channel, an over-expressed detoxifying enzyme — that lets them survive a dose. There is no equivalent mutation for protein denaturation. No bed bug population anywhere has developed heat resistance, and none is expected to, because the target is the fundamental chemistry of being alive.

Against that, heat has one significant weakness: it leaves nothing behind. A chemical residual keeps working for weeks after the technician leaves, while a heat treatment stops working the moment the room cools. Anything that walks back in afterwards from an adjoining unit is unopposed. That single asymmetry explains why most competent operators pair heat with a residual perimeter application rather than treating them as alternatives.

The thermal death curve

The thermal death point is not one temperature. It is a relationship between how hot it gets and how long it stays there, and the relationship is steep — a few degrees higher cuts the required exposure time dramatically.

The same data as a table, since the shape matters more than the exact points:

Sustained temperature	Adults	Eggs
113°F / 45°C	~90 minutes	Survive
118°F / 48°C	~20 minutes	Survive
122°F / 50°C	~8 minutes	~90 minutes, begin to fail
130°F / 54°C	Minutes	~12 minutes, all stages die
135°F / 57°C	Minutes	~5 minutes. Practical upper limit

Above 135°F the risk shifts from the insects to the contents, so operators hold the band rather than pushing higher. The number that counts is the temperature at the coldest point in the room, not the average.

Why eggs survive chemical treatment

Bed bug eggs survive chemical treatment for two structural reasons, and neither is a failing of the product.

First, the eggshell is a barrier. Most residual insecticides are formulated to be picked up on contact by an insect walking across a treated surface, and the shell does not reliably admit them. Second, an unhatched embryo does not walk anywhere. Residual products depend on the insect moving across the deposit, and an egg cemented into a seam never does.

So a competent chemical application can kill every mobile insect in a room and leave the next generation entirely intact. Those eggs hatch 6 to 10 days later, the bites resume, and the household concludes the treatment failed. It did not — it worked on everything it could reach. That is why a chemical programme is properly built as two or three visits timed around the hatch, and why judging a single application at day ten is judging it at exactly the wrong moment. The eggs guide covers that window in detail.

The equipment, and how the heat gets in

Three types of system are in common use, and they suit different properties.

Electric resistance heaters are placed inside the space and run off the building’s supply or a generator. They are clean, quiet, produce no combustion products, and are the usual choice for occupied apartments — but they draw heavily, and older Washington housing with limited electrical capacity frequently cannot support them without a generator outside.

Direct-fired propane systems burn fuel and blow heated air into the structure through ducting. They deliver far more heat far faster, which suits whole-home work and larger properties, and the burner stays outside with only ducting entering the building.

Hydronic systems heat glycol in an outdoor unit and circulate it through hoses to indoor exchangers. Slower, but with no combustion or airflow entering the living space at all, which matters in sensitive settings.

Whichever system, the heat still has to travel. Air movers are what actually make a treatment work — they force heated air into voids, under furniture, into drawers and through mattress cores. Radiant heating alone leaves cold pockets everywhere, and a technician who sets up heaters without also placing fans is not going to reach the target where it counts.

Monitoring, and the question worth asking

Monitoring is the difference between a treatment and an expensive warm afternoon. Competent operators place wireless remote probes at the points they expect to be coldest — inside mattress cores, behind headboards, in wall voids, under heavy furniture, at exterior wall junctions — and hold the target until those probes confirm it, not until the room-centre reading looks good.

Ask one question when you get a quote: where do you place your sensors, and how many? A company that answers immediately and specifically is running the job properly. A company that talks about the room temperature is heating air rather than killing insects.

Ask a second one about the hold time. A rapid rise followed by a short hold is the profile that produces survivors, because heat needs time to conduct into a mattress core or a wall void. The temperature at the probe is what matters, and it lags the air by a long way.

The four ways heat treatment fails

Heat treatment fails in four recognisable ways, and three of them are avoidable.

• Cold spots. Unmonitored voids, exterior wall junctions, and the floor under heavy furniture. This is the most common failure and it is a monitoring problem, not a heat problem.
• Clutter. Piles block airflow and create insulated pockets. Reducing clutter before treatment day matters more than cleaning does.
• Reinfestation from an adjoining unit. In multi-family buildings, treating one apartment thermally while the neighbour goes untreated invites reseeding through shared wall voids. This is why heat alone is often the wrong call in apartments.
• Items carried back in. Anything removed from the room before treatment and returned afterwards without being treated puts the infestation straight back.

That last one causes more repeat callouts than anything else, and it comes from a well-meant instinct — bagging up belongings and moving them to another room to protect them. Moving infested items around the house is the most reliable way to turn a one-room job into a whole-home one.

Where heat is the wrong choice

Heat is not always right, and a company that says so is telling you something useful. In occupied multi-unit buildings, shutting a floor down for a day is often impractical and the reinfestation risk is real. In older buildings with knob-and-tube wiring or limited service capacity, the equipment load may not be supportable. In senior living and assisted care, residents who cannot vacate for eight hours, oxygen equipment and medication storage requirements usually push the job toward a chemical or combined approach.

The chemical treatment guide covers what those programmes involve and where residual products still hold a genuine advantage. The heat treatment service page sets out the preparation list, what heat can damage, and Washington pricing in detail, and what treatment costs compares the two methods across every home type.

If you are still deciding, heat, chemical, steam or fumigation puts all four methods against the same five criteria, and the prep checklist is what you will need before treatment day either way.

Not every Washington exterminator carries thermal equipment, and coverage thins noticeably outside the Puget Sound corridor. Tell us where you are and we will say plainly whether heat is actually available there, rather than booking you a visit to find out.