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Plant health · PPE and biosecurity

PPPE: plant and personal protective equipment

Coveralls, hairnets, gloves and shoe covers give the worker protection from hazards, and they keep contamination from the worker away from the crop. The contamination is the particles, the microbes and the pests of the worker. A person is the primary source of contamination in each clean production space. This paper gives information about the quantity of contamination that a person releases. It also gives the minimum PPE for each production area and the equipment for each room. It gives the procedures for gowning and hand hygiene that stop contamination at the demarcation line between clean and dirty areas.

Plant health9 diagrams15 sources~17 min to read
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Purpose and scope

In a grow room, PPE is not only for you. In most rooms, the equipment gives protection to the plant from you. The contamination is the skin flakes that you release. It is also the spores on your jacket, the mites on your shoes and the viroid on your hands. The same coverall that keeps your clothing clean also keeps your contamination away from the crop. Thus the name is PPPE: plant and personal protective equipment.

Persons are typically the primary source of contamination in each clean space. The percentage is different in different facilities.[1] A person cannot stop the particles that the person releases. You can only put a barrier around the person and control the movement of the person through the building.

Terms

Definitions

PPE / PPPEPPE is personal protective equipment. PPPE is plant and personal protective equipment. The same equipment gives the crop protection from the person, and it gives the person protection from hazards.
Gowning / de-gowningGowning is the procedure to put on protective clothing (donning). De-gowning is the procedure to remove protective clothing (doffing). Do these procedures in a specified sequence, across the demarcation line between the clean area and the dirty area. Thus the contamination does not go across the demarcation line.
FomiteAn object with microbes on it, for example a phone, a pen, a door handle or a tool. The microbes can move from the object to your hands. Hands move contamination from the fomite to the crop.
BioaerosolParticles in the air that contain viable organisms. Examples are skin flakes with bacteria, fungal spores, and drops of liquid from a person who speaks or when a person flushes a toilet.
Cross-contaminationThe movement of contamination from a dirty area or item to a clean area or item. For example, a person goes from the room for the flowering stage to the propagation room and does not do the gowning procedure again.
Hierarchy of controlsThe legal sequence of the controls for risk: elimination, substitution, isolation, engineering controls, administrative controls, and then PPE as the last control.[15]
PCBUPerson Conducting a Business or Undertaking. PCBU is the NZ legal term for the business that has the duty (your employer) in HSWA.[14]
Reasonably practicableThe legal limit for the quantity of work that you must do. Compare the risk with the work and the cost of its control. You must control a risk when its effect is large and its cost of control is low.
Diagram of two gowning flows in a facility
Example. Two sets of PPE: one for cultivation, and a different set for post-harvest. Do not go into the dry room or the trim room in the coverall from the flowering room.Diagram for education
Quality of the information

Evidence and limitations

Three types of information

We want each paper to be correct. Thus we examine each paper for information that is not solid. This information comes from the view of one grower, from a small number of sources, or from grower methods that have no controlled test. We identify this information, and we do not show it as solid.

Frequently there is no paper for the decision that you must make. Then we use the reports of other growers and the methods that work in the rooms that we know. This information can help you, but it is not the result of a laboratory test. Use the methods that work for your plants, for your room and for your meters. If a table does not agree with your crop, use the data from your crop and record the difference.

Solid
Tests of plants, specifications or many sources that agree show that the information is correct
  • Persons are a primary vector of contamination. HpLVd can move on tools and on hands.
  • The log reductions for hand hygiene use a log scale. In test conditions, they are approximately 90%, 99% and 99.9%.
  • The flow of personnel is from clean to dirty areas. The flow of waste is from dirty areas to the exit.
Grower method
Many growers use this method in their rooms. Start with it, then change it for your room.
  • The sequence of gowning, and models with two kits, for cultivation and for post-harvest.
  • The NZ HSWA structure for PPE, where it is applicable.
Weak
The view of one grower, a small number of sources, one test, or a method that works in one room
  • One value of 70 to 90% for the part of cleanroom contamination that persons cause, as a constant for all conditions.
  • The contamination of a phone compared with a toilet seat, as an accurate measure of biosecurity.

If you find an error, make a report. We will correct it. Make the report on GitHub, with the name of the paper and the information that is incorrect. If you have a source, include it: Make a report of an accuracy problem. The regulations, labels and licenses of your area always override each procedure in these papers. The label weak in a paper shows the points where the risk of an error is highest.

The problem

Risks of contamination from personnel

A person in a cultivation room is the primary source of contamination in the space. The person releases particles, microbes and pests all the time, only because the person is in the room.

The quantity of contamination that a person releasesPersons are the primary source. All other sources are much smaller.~70-90%of the contamination in a cleanroom is from persons100k -> 5Mparticles each minute: no movement and fast movement37M + 7Mbacteria and fungi that a person releases into theair each hourapproximately 10 millionskin flakes each day, ~10% with viable bacteriaA person cannot stop the particles that the person releases. Thus PPE is a barrier around the person.
Figure 1. Persons are the primary source of contamination in a clean space.[1] A person releases approximately ten million skin flakes each day, and approximately a tenth of them have viable bacteria on them.[2] A room with persons receives tens of millions of bacteria and millions of fungal spores for each person each hour.[3]
  • Movement increases the quantity of particles. A person in a gown releases approximately 100,000 particles each minute when the person does not move. The person releases approximately a million when the person walks, and a maximum of five million when the person works fast.[1] Slow movement is a control.
  • Your phone is a fomite that you touch frequently. A phone has skin microbes and microbes from the environment on it. The phone goes to your head and back to your hands all day.[4]
  • Your shoes move pests and spores. The soles have viable pathogens and fungal spores on them. When you walk, the organisms on the floor go into the air again.[5] Mites and powdery mildew come into the room on clothing and footwear.
  • A toilet makes a plume of aerosol. When a person flushes the toilet, aerosol goes to a height of approximately 1.5 m (4.9 ft) in seconds. The aerosol stays viable for minutes to hours. A closed lid decreases the aerosol by a large quantity.[8]
The minimum

Minimum necessary PPE

You must use a baseline of PPE to go into each production area or handling area. Add the items for a specified room after this baseline. The baseline agrees with the personnel regulations for food GMP[9] and with the WHO good agricultural and collection practice[10].

  1. Clean outer clothing for this area only, which you put on at the entrance (gown, smock, scrubs or coverall). Do not use your street clothes.
  2. Hair and beard cover. Put a bouffant or a hairnet on all of your hair. Put a beard cover on facial hair.
  3. Single-use nitrile gloves. Use gloves that have no damage. Replace a glove when it has damage or contamination.
  4. Footwear for this area only: room shoes or shoe covers. Do not use the boots that you wore in the parking area.
  5. Hand hygiene. Do hand hygiene at the entrance, after contamination and after you are away from the area.
  6. No personal items. Keep your phone, jewelry, watch and makeup in a locker before you go into the area.
Table of log reductions for hand hygiene
Example. Log reduction: 1 log reduction is approximately 90%, 2 log reductions are approximately 99%, and 3 log reductions are approximately 99.9%. The value of 83% for 3 log reductions is incorrect.Diagram for education
Each room

PPE for each room

The grade of PPE is different for each room, because the value of the contents and the risk to the contents are different. Do not use the same PPE in all rooms. Use the highest grade where the genetics are, and where the product is open and goes to a patient.

The grade of PPE for each roomUse the highest grade where the genetics are and where the product is openVault /storagegloves, securityTrim /packaginghairnet, beardnet, gloves,smockVegetative /floweringgown, hairnet,gloves, roomshoesDry /curecleanroom gown,open productMother /propagationfull gown, newgloves each plantTissue-culturelabsterile gloves,lab coat, ISO-5hoodbar height = PPE gradeExtraction is different: PPE gives protection to the worker (FR clothing, goggles, respirator)
Figure 2. The grade of PPE increases from the vault to the tissue-culture lab. Mother rooms and propagation rooms have the highest biosecurity, because each plant that you propagate from one infected plant has the infection.[6]
Persons must go through the rooms in sequence, from clean to dirty. They go to propagation rooms and mother rooms first, before they go to the rooms for the flowering stage or to post-harvest areas.
ZonePPE gradePrimary items
Tissue-culture labAseptic / ISO-5Scrub the arms to the elbows. Use sterile gloves and a lab coat. Work in a laminar-flow hood. Do not use jewelry.
Mother / propagationHighest biosecurityFull gown. New gloves for each plant. Tools for this room only. Work in this room first in the day.
Dry / cureCleanroom gradeThe product is open, and the microbial specification is a release gate.
Vegetative stage / flowering stageStandard gownGown, hairnet, gloves, footwear for this room only, sticky mat at the door
Trim / packagingFood-contact gradeHairnet, beard net, gloves, smock. Change the gloves frequently.
Vault / storageMinimum (security)Gloves to keep the product clean. The controls are mostly for security.
The procedure

Gowning procedure

The sequence is important. Put on the PPE from the top to the bottom. Thus the particles that you release when you put on the clothing fall on parts of the body that have no clothing at this time. At the same time, you go across the demarcation line between the dirty area and the clean area.[13]

Gowning sequence: from the top to the bottom, the dirtiest items lastParticles fall on parts of the body with no clothing. Put on the clothing for the top first.1Remove the phone, jewelry, watch and makeup2Hairnet or bouffant and beard cover3Face mask, then eyewear4Inner gloves5Coverall and hood. Keep the coverall off the floor.6Boot covers, when you go across the demarcation line7Outer gloves on the cuffs of the coverall8Sanitize your hands and go inDe-gowning, dirtiest first: outer gloves, boot covers, coverall (inside-out), eyewear, hood, mask (loops only), hairnet, inner gloves. Then wash.
Figure 3. Do the gowning in this sequence. Remove personal items, then put on the hair cover and the beard cover. Put on the mask and the eyewear, then the inner gloves, then the coverall and the hood. Put on the boot covers when you go across the demarcation line. Put the outer gloves on the cuffs of the coverall. Sanitize your hands and go in.[13]
The procedure

Hands and gloves

Hands move most of the contamination from one area to a different area. Thus hand hygiene is the task that you do most frequently in the building. Do hand hygiene at the entrance, and before clean work or aseptic work. Do it also after waste or contamination, after you are away from the area, and when you go in again.[11]

Hand hygiene: the method and the timesSoap and alcohol rub do not sterilize the hands. Thus you do hand hygiene frequently and not one time.1Water and soap→2Palm to palm→3Between thefingers→4Back of thehand→5Thumbs→6Fingertips andnailsSoap and water 40 to 60 seconds (for dirty hands) · Alcohol rub 20 to 30 seconds (minimum 60% alcohol)When: at entry, before clean work or aseptic work, after waste or contamination, after you are away from the area, when you go in again.Approximately: an alcohol rub removes 83% (3 log) and a hand wash 58% (2 log). Some organisms stay: do it at each change of area.
Figure 4. The method is for all surfaces of the hand: palms, the spaces between the fingers, the back of the hand, thumbs, fingertips and nails. When the hands are dirty, use soap and water for 40 to 60 seconds. When the hands are not dirty, use an alcohol rub with a minimum of 60% alcohol for 20 to 30 seconds.[11]
Remove the gloves and do not touch the dirty sideFirst, a glove touches a glove. Then, skin touches skin.1Hold the outersurface of one cuffglove touches glove only→2Remove itinside-out, hold itin the hand with a glove→3Put bare fingers inthe other cuffremove it with the firstglove in it, then washGloves do not replace hand hygiene: wash before and immediately after you use them. Bare skin does not touch the outer surface.
Figure 5. The gloves are the most contaminated item. Remove them first, inside-out. First, a glove touches a glove. Then, skin touches skin. Thus bare skin does not touch the dirty outer surface.[12]
The problems of each day

Frequent errors of compliance

Phones and personal items

Do not put phones, earbuds, jewelry, watches or makeup into production areas or clean areas. A phone is a fomite that you hold to your head, and you cannot clean it.[4] Put all of these items in lockers before you go into the gowning room.

The toilet

A toilet must not have a door into a production area. When a person flushes a toilet, viable bioaerosol goes to a height of more than 1 m (3 ft) in seconds.[8] Thus a person who comes back from the toilet can move contamination into the area. The risk continues until the person washes the hands and does the gowning procedure again.

The toilet is not in the clean areaThe plume of a flush goes to a height of approximately 1.5 m in 8 seconds and stays viable for minutesDe-gowningbefore the toilet→Use the toiletlid down: ~12times less aerosol→Wash your handssoap, 40 to 60 s→Wash and sanitizewhen you come back→Gowning againclean clothing, goin againA toilet must not open into production. A person from the toilet can move bioaerosol until the person washes and does the gowning again.
Figure 6. Do the de-gowning procedure before you go to the toilet. Close the lid before you flush. Wash your hands. When you come back, wash and sanitize your hands again. Then put on clean clothing before you go into the area again.[8]

Food, drink and break areas

Do not eat, drink, use chewing gum or use an electronic cigarette in a production area. Before you go to a break area, do the de-gowning procedure. When you come back, wash your hands and do the gowning procedure again.

Footwear and the floor

Stop the contamination that comes in on shoesShoes and floors are a primary source of spores and pestsdemarcation lineDIRTY sideCLEAN sideDirty shoeSticky mat~99% at 0.5 µmFootbath(quat or H2O2)Boot for this room onlyor shoe cover, go acrossRemove the shoes on the dirty side. Put on the room boots at the demarcation line. Do not move soles to the clean side.
Figure 7. The controls at the threshold have layers. A sticky mat removes most of the particles from the shoes. A footbath disinfects the shoes. You put on the boots or shoe covers for the room when you go across the demarcation line.[5]

Cross-contamination: flow in one direction

Flow in one direction: from dirty to clean, not backPersons, materials and waste move in one direction onlyDirty area /lockersGowningairlockCleanproductionProductexitdemarcation line: a dirty hand does not touch the clean sidego back: do the gowning procedure againFiltered air with higher pressure in the clean area flows to the dirty area. Thus dirty air does not go to the canopy.
Figure 8. Move persons and clean materials from the clean area to the dirty area. Move waste and used PPE only from the dirty area to the exit. Do not go back. If a person goes back, the person must do the gowning procedure again. A hand or a sleeve from the dirty side must not touch the clean side.
Regulations (NZ)

Duties in HSWA 2015

In New Zealand, PPE and hygiene are legal duties in the Health and Safety at Work Act 2015 (HSWA). They are not only good procedures.[14] WorkSafe monitors the compliance with these duties.[15]

PPE is the last control, not the firstThe NZ regulations tell you to apply the higher controls before you use PPEEliminationremove the hazardSubstitutionuse a safer itemIsolationkeep persons away from itEngineering controlsbarriers, airflow, roomsAdministrative controlsSOPs, training, signsPPElast control, with the other controlshighlowprotection
Figure 9. The regulations tell you to control risk with the hierarchy of controls. You must use PPE as the last control, after elimination, substitution, isolation, engineering controls and administrative controls.[15]
The business (PCBU) must
  • Make sure of the health and safety of workers, as far as is reasonably practicable (s36).
  • Apply the higher controls before you use PPE.
  • Supply PPE and replacements. Make sure that the workers have no cost for PPE (s27).
  • Give information, training, supervision and sufficient facilities.
Workers must
  • Use reasonable care for their safety and for the safety of other persons (s45).
  • Obey the reasonable instructions. Put on the necessary PPE. Obey the SOPs for gowning and hygiene.
  • Do not use safety items incorrectly. Do not change them or cause damage to them.
  • Visitors have the same duties: use reasonable care and obey the instructions.
Short list

Reference list

Baseline for each room
Gown, hairnet and beard net, gloves, room shoes, wash the hands, no personal items
Gowning sequence
Hair, then mask, then eyewear, then inner gloves, then coverall, then hood, then boot covers, then outer gloves
De-gowning
Opposite sequence, dirtiest item first, then wash the hands
Hand wash
Soap: 40 to 60 seconds. Alcohol rub: 20 to 30 seconds (minimum 60% alcohol).
Gloves
Remove first, inside-out. Wash your hands also when you use gloves. In propagation, new gloves for each plant.
Phones
Do not put phones into clean areas. Use lockers before the gowning room.
Toilet
Do the de-gowning procedure. Close the lid. Wash the hands. When you come back, wash and sanitize the hands. Do the gowning procedure again.
Flow
Persons and materials: from clean to dirty. Waste: from dirty to the exit. To go back, do the gowning procedure again.
Regulations (NZ)
The PCBU supplies PPE at no cost to workers (s27). PPE is the last control.

References

  1. Cleanroom contamination analyses: personnel are typically the dominant contamination source (industry figures often cite a large majority; exact share varies by facility); a gowned worker emits ~100,000 particles/min at rest, ~1,000,000 walking, up to ~5,000,000 in active work. (source not from a journal, for example from a manufacturer). https://www.precgroup.com/70-percent-of-cleanroom-contamination/
  2. Noble / CDC Emerging Infectious Diseases: humans disseminate ~10^7 skin squames per day, of which roughly 10% carry viable bacteria. https://wwwnc.cdc.gov/eid/article/7/2/70-0225_article
  3. Human microbial-emissions research: an occupied space gains roughly 37 million bacterial and 7 million fungal genome copies per person per hour above the unoccupied baseline. https://pmc.ncbi.nlm.nih.gov/articles/PMC7950481/
  4. Mobile phones as fomites: high-touch devices carry skin and environmental flora (methods and comparisons vary across studies), isolates including S. aureus, E. coli and Candida. https://pmc.ncbi.nlm.nih.gov/articles/PMC3939586/
  5. Shoe-sole and floor contamination: soles carry MRSA, C. difficile, E. coli and other organisms; walking re-disperses settled organisms, contributing a meaningful share of airborne CFU. (source not from a journal, for example from a manufacturer). https://www.infectioncontroltoday.com/view/shoe-sole-and-floor-contamination-new-consideration-environmental-hygiene
  6. Mechanical transmission and management of Hop Latent Viroid (HLVd) in cannabis: spread via contaminated tools and cuttings; under experimental conditions linked cuttings can approach complete infection within weeks; controls include fresh gloves per plant, tool sterilisation and footbaths. Plants (MDPI) 2025, 14:830. https://www.mdpi.com/2223-7747/14/5/830
  7. Comparative hand-hygiene efficacy: alcohol-based handrubs often achieve ~2–3 log reductions of transient flora under test conditions (~99–99.9%); soap and water remove soil and many organisms but neither sterilises hands. (Note: 1 log ≈ 90%, not ~58–83%.). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC117885/
  8. Toilet-flush bioaerosol ('toilet plume'): a flush lofts aerosols to ~1.5 m within seconds; particles remain viable for minutes to hours, and a closed lid produces markedly less aerosol. https://pmc.ncbi.nlm.nih.gov/articles/PMC9732293/
  9. US FDA. 21 CFR 117.10, Personnel (current good manufacturing practice for food): clean outer garments, personal cleanliness, hand washing, hair restraints, glove integrity. (source not from a journal, for example from a manufacturer). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-117/subpart-B
  10. World Health Organization (2003). WHO guidelines on good agricultural and collection practices (GACP) for medicinal plants. (source not from a journal, for example from a manufacturer). https://www.who.int/publications/i/item/9241546271
  11. World Health Organization. Hand hygiene: the Five Moments and recommended technique (soap-and-water 40-60s; alcohol-based handrub 20-30s, ≥60% alcohol). (source not from a journal, for example from a manufacturer). https://www.who.int/teams/integrated-health-services/infection-prevention-control/hand-hygiene
  12. US CDC. How to safely remove gloves: glove-to-glove then skin-to-skin, peeling inside-out so bare skin never contacts the contaminated exterior; hand hygiene before and after. (source not from a journal, for example from a manufacturer). https://www.cdc.gov/ebola/media/pdfs/2024/05/poster-how-to-remove-gloves.pdf
  13. GMP / cleanroom gowning and de-gowning procedures: top-to-bottom donning order across a clean/dirty demarcation bench, reverse dirtiest-first removal. (source not from a journal, for example from a manufacturer). https://www.pharmanow.live/pharma-manufacturing/cleanroom-gowning-procedures-guide
  14. Health and Safety at Work Act 2015 (NZ): s36 PCBU primary duty of care; s45 worker duties; s27 PCBU must provide what is required (including PPE) and must not charge workers for it. (source not from a journal, for example from a manufacturer). https://www.legislation.govt.nz/act/public/2015/0070/latest/DLM5976894.html
  15. WorkSafe New Zealand and the Health and Safety at Work (General Risk and Workplace Management) Regulations 2016, reg 6: control risk by the hierarchy of controls, with PPE as the last resort. (source not from a journal, for example from a manufacturer). https://www.worksafe.govt.nz/managing-health-and-safety/getting-started/introduction-hswa-special-guide/

The Cannabis White Papers · CC BY-NC 4.0 · version 1.2 · updated 2026-07-18