Short answer
Enzyme and microbial products can help by breaking down dried blood on hard or slightly absorbent surfaces like grout, concrete and sealed wood. They can also cut lingering odor. They are cleaners, not disinfectants, unless a product's EPA registration says otherwise. They come after the bulk of the material is removed and before disinfection. They will not save carpet, mattresses or drywall that blood has soaked.
What do people mean by bioremediation at a crime scene?
In environmental work, bioremediation usually means using tiny living organisms to break down pollution in soil or water. In crime scene cleanup, the word is used more loosely. Most of the time it means two kinds of products. Enzyme cleaners contain proteins that break apart blood and other organic matter. Microbial or bacterial cleaners contain live, helpful microbes that digest residue over time.
Both can be useful tools in your cleanup. Neither is magic. Neither replaces the core work: removing blood, disposing of soiled materials and disinfecting cleaned surfaces with a registered product.
The word bioremediation sounds scientific, so it sometimes shows up in sales material without much explanation. Once you know what these products really do, you can judge whether they belong in your written work plan.
How enzyme cleaners break down blood
Blood is rich in proteins. As it dries, those proteins bind tightly to surfaces and to each other. That is why old blood stains resist ordinary detergents. Enzyme cleaners often contain proteases. These are enzymes that cut protein chains into smaller pieces that can be lifted and rinsed away.
That makes enzymes a real help on rough and slightly absorbent surfaces where scrubbing alone struggles. Examples are grout lines, unsealed concrete, brick, textured tile and the edges of sealed wood floors. They also include some fabric furniture that is being cleaned and not thrown away. Enzymes can help in the cracks and seams inside a vehicle too.
Enzymes need time, moisture and the right temperature to work. If you spray a product on and wipe it off right away, it will do little. A trained crew follows the label for how long the product must sit. They keep the surface damp, then scrub and rinse.
Enzymes are most valuable where blood has dried for days. On a sealed tile floor cleaned within hours of the police release, a good detergent may do the job. On a concrete patio where blood sat through several warm afternoons, an enzyme cleaner often does better. The extra soaking time and protein-breaking action can mean a truly clean surface, not a faint shadow.
Cleaners, not disinfectants, and the order of use
Enzyme and microbial cleaners break down organic soil. They are not made to kill germs such as hepatitis B, hepatitis C or HIV. A product may be sold with disinfection claims only if it is registered for those claims. Under FIFRA, EPA must register every pesticide sold or distributed in the United States, and disinfectants count as pesticides. FIFRA is the federal pesticide law.
That is why your work plan should list a separate disinfection step. It should use an EPA-registered product suited to germs carried in blood. The crew should apply it by the label and keep the surface wet for the time the label requires. The enzyme step makes that disinfection work better. It removes the organic material that would otherwise shield germs.
If a company tells you an enzyme or bacterial cleaner kills everything, ask to see the product's EPA registration and label. If it is not registered as a disinfectant, it should not be presented as one.
Some products combine a cleaning action with a registered disinfectant claim in one formula. These can be a fine choice for your job, but only for the germs, surfaces and wet times listed on the label. Many still require a cleaning step first when heavy soil such as dried blood is present. Go by the directions, not the product name.
Order matters. Many disinfectants are made to be harsh on proteins and living cells. So they can shut down enzymes and kill helpful microbes. Using both at the same time wastes both products.
A typical order of steps at a crime scene looks like this. Every job is different, and the labels always rule.
- Close off the area and remove the bulk of the material and soiled soft items
- Apply the enzyme cleaner to affected hard or slightly absorbent surfaces and leave it for the time on the label
- Scrub, then rinse or suck up the residue with as little water as possible
- Check for stains that remain and repeat the enzyme step if needed
- Apply an EPA-registered disinfectant and keep surfaces wet for the full time the label requires
- Rinse or wipe as the disinfectant label directs, then dry and record the work
Limits: saturated materials, residue and odor
Enzymes cannot reach blood that has soaked deep into the soft or absorbent materials in your home. Carpet pad, mattresses, padded cushions, pillows and drywall that soaked up blood usually need to be removed and disposed of as regulated waste. Trying to treat them in place with enzymes can leave blood behind and cause odor later.
Microbial products that rely on live bacteria can be a poor fit in a home where someone has a weak immune system. They also need time, sometimes days, to finish their work. Ask your cleanup company whether a live-culture product is needed, or whether an enzyme-only product would do the same job.
Enzymes are also no cure for police residue. Fingerprint powders and test chemicals need their own cleaning methods. Those often begin with a HEPA vacuum, which traps very fine dust.
Finally, enzymes should not be a reason to leave doubtful materials in place. A worker may be unsure whether blood reached the underside of a wood floor or the back of a baseboard. The right step is to open it up and look. A product applied to the surface cannot answer that question.
Most crime scenes that are cleaned soon after the police release do not have a strong odor. If your scene sat for several days, especially in warm weather, blood residue in cracks and seams can produce an unpleasant smell. Enzyme cleaners can help by breaking down the residue that causes it. They do not just cover it with fragrance.
If you still notice the odor after enzyme treatment and disinfection, some source material is still there. It is often under flooring, inside a wall or in a piece of furniture. The answer is more inspection and removal, not more product.
Ask your cleanup company how it will judge whether the odor is gone and what it will do if the smell returns.
Vehicles are a common exception. If your car or truck was used in or affected by a crime, it can hold odor in seat seams, carpet and the air vents, even when the incident was recent. The space is small and heats up quickly. Enzymes often play a larger role there. They are used along with removing seat covers or carpet sections that soaked up blood.
Are these products safe to use around my family and pets?
Mostly, with care. Enzyme cleaners are generally seen as milder than many disinfectants, which is part of their appeal in homes. Milder does not mean harmless, though. Some people are sensitive to enzyme dusts or mists, and strong products can irritate skin and eyes. Crews wear the same protective gear they would for any blood cleanup. They do so because of the product and because of the blood they are removing.
Live-culture microbial products raise a different question. The microbes in them are chosen because they are not considered harmful to healthy people. But your household may include someone in cancer treatment, an organ transplant recipient or a person with another serious immune condition. If so, you may prefer to avoid these products. Tell the cleanup company about anyone in your household with special health concerns before work begins.
Keep your pets out of treated areas until surfaces are rinsed, disinfected and dry. Animals lick their paws and the floor. Residue from any cleaning product is best kept away from them.
Ask for safety data sheets for every product. A reputable company will hand them over without hesitation. It will also explain how long you should wait before you use the space again.
Questions to ask a company about enzymes and microbes
Ask which surfaces the company plans to treat with enzyme or microbial products, and why. Ask what product it will use and whether it contains live cultures. Ask what the label says about how long the product must sit. Ask how it keeps the enzyme step apart from disinfection and which registered disinfectant it will use afterward.
Ask whether anyone in your household should stay away during treatment, especially someone with breathing or immune concerns. And ask how the products and rinse water will be disposed of. If you are unsure what may go down a drain, your local wastewater utility can tell you.
Look for a company that explains these points clearly to you and never suggests that a biological cleaner replaces removal or disinfection. That company is using these tools the way they are meant to be used.
