The evidence
Each criterion with what we found, where we found it and when. Anything we could not confirm says so.
NTH criteria
NTH Framework v1.2. Score 37.1 (raw 28.0 of 100), calibrated so the best hotel in this edition (Santa Monica Proper Hotel) reads 90. Evidence retrieved 2026-10-22.
Sleep6.4 / 24
The room as an instrument for deep, uninterrupted, circadian-aligned rest.
Mattress & sleep system
Hotel-reported · in the best room
Hypnos mattress; materials not described.
Bedding & textiles
Hotel-reported · in the best room
Hypoallergenic bedding available.
Sleep programme & pillow menu
Hotel-reported · in the best room
Pillow menu.
Blackout
Hotel-reported · in the best room
Blackout drapes.
Circadian & warm evening lighting
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
In-room red light
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Acoustic quiet
Hotel-reported · in the best room
Soundproofed rooms.
EMF & Wi-Fi-off options
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Air0.0 / 12
What you breathe for eight hours a night: filtered, fresh, smoke-free and unperfumed.
In-room purification
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 5 pts
Unknown
Ventilation & building standard
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 3 pts
Unknown
Smoke-free policy
Hotel-reported · across the property
Third-party listing shows 'Smoking and Non-Smoking'; confirm with hotel.
Fragrance-free & low-allergen rooms
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Water0.0 / 12
Clean water to drink, and to shower and bathe in.
Filtered drinking water
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 5 pts
Unknown
Shower & bath filtration
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 5 pts
Unknown
Gentler pool & hydrotherapy water
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Nourishment4.0 / 10
Food and drink that heal rather than merely please.
Organic & local sourcing
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 4 pts
Unknown
Clean-ingredient standard
Hotel-reported · across the property
Biome Lounge menu created with nutrition scientist Dr Federica Amati.
Clean minibar & in-room hydration
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Nutrition guidance
Hotel-reported · across the property
Registered nutritionist on the Biome roster.
Movement7.6 / 10
The means to train, stretch and move, indoors and out.
Gym completeness
Hotel-reported · across the property
Gym 24/7; Peloton, Technogym, BLK BOX.
Classes & studios
Hotel-reported · across the property
Complimentary classes.
Swimming
Hotel-reported · across the property
Swimming pool.
Outdoor activity
Hotel-reported · across the property
Free bicycle rentals.
Holistic Wellness8.0 / 19
Healing traditions and the recovery technology that complements them.
Spa facility
Hotel-reported · across the property
17 treatment pods; amphitheatre sauna, steam room, vitality pool.
Traditional & integrative modalities
Hotel-reported · across the property
Head Osteopath; eco-psychologist and nature therapy.
Mind & breath
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Heat therapy
Hotel-reported · across the property
Amphitheatre sauna, Biome Sync Sauna, steam.
Cold therapy
Hotel-reported · across the property
Cold plunge; ice fountain.
Photobiomodulation & PEMF
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Clinical longevity (IV, HBOT, diagnostics)
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 4 pts
Unknown
Materials & Setting2.0 / 13
What touches the skin and surrounds the stay: finishes, products, cleaning, and the landscape beyond the door.
Natural, low-VOC finishes
Not yet reviewed · in the best room
Unknown. We have asked the hotel.
0.0 / 3 pts
Unknown
Clean bath & body amenities
Hotel-reported · in the best room
Wildsmith Skin bathroom products.
Non-toxic spa & nail products
Hotel-reported · across the property
Wildsmith Skin, a tree-inspired brand guided by circadian principles.
Non-toxic housekeeping & plastic-free operations
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Green & blue space
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Walkability & low-impact mobility
Not yet reviewed · across the property
Unknown. We have asked the hotel.
0.0 / 2 pts
Unknown
Our review
At a glance
- Fragrance
- 5 not yet reviewed
- Air
- 1 not met, 4 not yet reviewed
- Cleaning & care
- 4 not yet reviewed
- Sleep & materials
- 5 not yet reviewed
- Water & pools
- 4 not yet reviewed
- Food
- 2 not yet reviewed
- Light & quiet
- 2 not yet reviewed
- Building
- 3 not yet reviewed
One not met; the rest not yet reviewed.
1 not met24 of 25 not yet reviewed
Counts cover the 25 scored criteria; the other 5 windows are context.
Checked
Read the full profileThe ledger
Fragrance
Added scent is the most common complaint from sensitive guests, and the hardest thing to see on a booking page.
No added fragrance in rooms
Not yet reviewed.
No scent marketing
Not yet reviewed.
Fragrance-free laundry
Not yet reviewed.
Unscented bath products
Not yet reviewed.
So far, the hotel says: Rooms have ‘Luxurious Wildsmith Skin bathroom products’.
Our note. Whether these are scented, and whether an unscented option is offered, is not stated.
How we know
What we look for. Fragrance-free toiletries in the room by default, or on request.
Why it matters. Fragrance ingredients are among the most frequent causes of allergic contact reactions to cosmetics. An unscented option lets sensitive guests use what is provided instead of packing their own.
Source: EU Scientific Committee on Consumer Safety, Opinion on fragrance allergens in cosmetic products ()
Source 1: Hotel website: hotel facilitiesUndated · read 22 Oct 2026
Unscented spa options
Not yet reviewed.
So far, the hotel says: The Biome Sync Sauna includes ‘aromatic towel waving to infuse botanicals into the air’ and ends with a mist of English rose and calendula.
Our note. This is one guided session. Whether the amphitheatre sauna and steam room are used without scent at other times, and which treatments can be done without essential oils, is not stated.
How we know
What we look for. Treatments, saunas and steam rooms available without essential oils or scent infusions.
Why it matters. Essential oils are fragrance: the EU’s scientific committee lists several natural extracts, as well as single fragrance chemicals, among established contact allergens. A shared sauna with a scent infusion is hard to avoid.
Source: EU Scientific Committee on Consumer Safety, Opinion on fragrance allergens in cosmetic products ()
Source 2: Hotel website: Biome spaUndated · read 22 Oct 2026
Know something about fragrance here that we don’t? Tell us
Air
What you breathe for eight hours a night: smoke history, fresh air, filtration and anything burning in the room.
Smoke-free property
Not metin some rooms or areas
The hotel says: The Garden, the hotel’s outdoor terrace restaurant, lists ‘Non-smoking hours: 12noon - 3pm, 6pm - 9pm’; the hotel’s facilities page says it has a cigar humidor.
Our note. This covers the terrace restaurant. The hotel does not publish a smoking policy for guest rooms, so ask for a room that has never been a smoking room.
How we know
What we look for. No smoking in any guest room, balcony or indoor space.
Why it matters. Tobacco smoke leaves a residue (thirdhand smoke) on surfaces and in dust. A study of California hotels found that non-smoking rooms in hotels that allow smoking elsewhere did not protect non-smoking guests from it.
Source: Matt et al., Tobacco Control, Thirdhand smoke and exposure in California hotels: non-smoking rooms fail to protect non-smoking hotel guests from tobacco smoke exposure ()
Source 3: Hotel website: The GardenUndated · read 22 Oct 2026
Opening windows
Not yet reviewed.
So far, the hotel says: ‘Select rooms feature Juliette balconies.’
Our note. Stated for select rooms only, and the hotel does not say which.
How we know
What we look for. Guest rooms have windows or doors that open to outside air.
Why it matters. The US EPA lists opening windows, when outdoor air allows, as a way to dilute pollutants released indoors. An opening window lets guests air a room themselves when it smells of cleaning products or new furnishings.
Source: US EPA, Improving indoor air quality ()
Source 4: Hotel website: rooms and suitesUndated · read 22 Oct 2026
Filtered fresh air
Not yet reviewed.
In-room air purifier
Not yet reviewed.
No in-room combustion
Not yet reviewed.
So far, the hotel says: The Writer’s Penthouse has a ‘double-height lounge with fireplace’ and the Garden Suite a ‘decorative fireplace’.
Our note. Whether either burns gas or is purely decorative is not stated. Candles and incense are not mentioned.
How we know
What we look for. No gas fireplaces, candles or incense in guest rooms.
Why it matters. In homes with gas appliances, the US EPA notes that indoor nitrogen dioxide often exceeds outdoor levels, and that it irritates the eyes, nose, throat and airways. Candles and incense burn in the same small, closed room.
Source: US EPA, Nitrogen dioxide’s impact on indoor air quality ()
Source 4: Hotel website: rooms and suitesUndated · read 22 Oct 2026
Know something about air here that we don’t? Tell us
Cleaning & care
How a room is cleaned, treated and prepared, and whether a request for a gentler clean is actually honored.
Low-chemical housekeeping
Not yet reviewed.
No ozone or biocide treatments
Not yet reviewed.
Low-chemical pest control
Not yet reviewed.
Sensitive-guest preparation
Not yet reviewed.
Know something about cleaning & care here that we don’t? Tell us
Sleep & materials
The textiles, mattress and floor you spend the night closest to, and how allergen-aware the room is.
Tested or organic bed linen
Not yet reviewed.
Mattress materials disclosed
Not yet reviewed.
So far, the hotel says: Superior and Executive rooms have a ‘King bed with Hypnos mattress’; the Trafalgar, Whitehall and Garden Suites have a Hästens mattress.
Our note. The brands are named, but the materials and how flame-retardancy is achieved are not.
How we know
What we look for. The hotel says what its mattresses are made of and how flame-retardancy is achieved.
Why it matters. Flame retardants have been added to mattresses and seating foam, and the US National Institute of Environmental Health Sciences lists possible effects including endocrine and thyroid disruption. How much a mattress adds to anyone’s exposure is still debated; disclosure lets guests choose.
Source: US National Institute of Environmental Health Sciences, Flame retardants (undated)
Source 4: Hotel website: rooms and suitesUndated · read 22 Oct 2026
Hard floors
Not yet reviewed.
Allergy-friendly rooms
Not yet reviewed.
Pet-free rooms
Not yet reviewed.
Know something about sleep & materials here that we don’t? Tell us
Water & pools
Drinking water, shower water and pool air.
Filtered or tested drinking water
Not yet reviewed.
Water safety plan
Not yet reviewed.
Shower filters
Not yet reviewed.
Shown for information; not scored.
Outdoor or low-chloramine pools
Not yet reviewed.
So far, the hotel says: Biome has a swimming pool, a vitality pool and an ice fountain; the spa page also lists a cold plunge.
Our note. The pools are indoors, and their ventilation and water treatment are not described.
Shown for information; not scored.
How we know
What we look for. Pools are outdoors, or indoor pools have dedicated ventilation and monitored combined chlorine.
Why it matters. Chloramines irritate the skin, eyes and airways, and they build up in the air of indoor pools without enough ventilation. Outdoor pools, and good ventilation for indoor ones, keep levels low.
Source: US CDC, Chloramines and pool operation ()
Source 1: Hotel website: hotel facilitiesUndated · read 22 Oct 2026
Context, not scored: almost every pool in this catalog is outdoors, so it says little about one hotel against another.
Know something about water & pools here that we don’t? Tell us
Food
Allergen care first; where the produce comes from second.
Allergen-aware kitchen
Not yet reviewed.
Garden or organic produce
Not yet reviewed.
Shown for information; not scored.
Know something about food here that we don’t? Tell us
Light & quiet
Darkness and silence at night, and radio-quiet options for guests who want them.
Darkness and quiet
Not yet reviewed.
Radio-quiet options
Not yet reviewed.
Shown for information; not scored.
Know something about light & quiet here that we don’t? Tell us
Building
The materials a hotel was built and renovated with, how it handles damp, and what third parties have certified.
Low-emitting materials
Not yet reviewed.
Leak and mold response
Not yet reviewed.
Building certification
Not yet reviewed.
Shown for information; not scored.
Know something about building here that we don’t? Tell us
Notes & sources
- Hotel website: hotel facilities, Undated · read 22 Oct 2026
- Hotel website: Biome spa, Undated · read 22 Oct 2026
- Hotel website: The Garden, Undated · read 22 Oct 2026
- Hotel website: rooms and suites, Undated · read 22 Oct 2026
- Wikipedia: Corinthia Hotel London, Undated · read 22 Oct 2026
Room count: Per the hotel’s website, including 62 suites and seven penthouses. Hotel website (opens the hotel’s website)
Photographs: Corinthia London; Corinthia London; Corinthia London; Corinthia London; Corinthia London; Corinthia London
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